CI: add W=1 option to SOF compilation #405

  WARNING: Symbol version dump ./Module.symvers
           is missing; modules will have no dependencies and modversions.

  CC [M]  sound/soc/sof/intel/byt.o
  LD [M]  sound/soc/sof/intel/snd-sof-intel-byt.o
  CC [M]  sound/soc/sof/intel/hsw.o
  LD [M]  sound/soc/sof/intel/snd-sof-intel-hsw.o
  CC [M]  sound/soc/sof/intel/bdw.o
  LD [M]  sound/soc/sof/intel/snd-sof-intel-bdw.o
  CC [M]  sound/soc/sof/intel/hda.o
  CC [M]  sound/soc/sof/intel/hda-loader.o
  CC [M]  sound/soc/sof/intel/hda-stream.o
  CC [M]  sound/soc/sof/intel/hda-trace.o
  CC [M]  sound/soc/sof/intel/hda-dsp.o
  CC [M]  sound/soc/sof/intel/hda-ipc.o
  CC [M]  sound/soc/sof/intel/hda-ctrl.o
  CC [M]  sound/soc/sof/intel/hda-pcm.o
  CC [M]  sound/soc/sof/intel/hda-dai.o
sound/soc/sof/intel/hda-dai.c: In function ‘hda_link_hw_free’:
sound/soc/sof/intel/hda-dai.c:213:22: warning: variable ‘sdev’ set but not used [-Wunused-but-set-variable]
  struct snd_sof_dev *sdev;
                      ^~~~
  CC [M]  sound/soc/sof/intel/hda-bus.o
  CC [M]  sound/soc/sof/intel/hda-loader-skl.o
  CC [M]  sound/soc/sof/intel/skl.o
  CC [M]  sound/soc/sof/intel/apl.o
  CC [M]  sound/soc/sof/intel/cnl.o
  LD [M]  sound/soc/sof/intel/snd-sof-intel-hda-common.o
  CC [M]  sound/soc/sof/intel/hda-codec.o
  LD [M]  sound/soc/sof/intel/snd-sof-intel-hda.o
  CC [M]  sound/soc/sof/xtensa/core.o
  LD [M]  sound/soc/sof/xtensa/snd-sof-xtensa-dsp.o
  CC [M]  sound/soc/sof/core.o
  CC [M]  sound/soc/sof/ops.o
  CC [M]  sound/soc/sof/loader.o
  CC [M]  sound/soc/sof/ipc.o
  CC [M]  sound/soc/sof/pcm.o
  CC [M]  sound/soc/sof/pm.o
  CC [M]  sound/soc/sof/debug.o
sound/soc/sof/debug.c: In function ‘sof_dfsentry_read’:
sound/soc/sof/debug.c:62:10: warning: comparison of unsigned expression < 0 is always false [-Wtype-limits]
  if (ret < 0)
          ^
  CC [M]  sound/soc/sof/topology.o
sound/soc/sof/topology.c: In function ‘sof_control_load_volume’:
sound/soc/sof/topology.c:261:28: warning: variable ‘cdata’ set but not used [-Wunused-but-set-variable]
  struct sof_ipc_ctrl_data *cdata;
                            ^~~~~
sound/soc/sof/topology.c: In function ‘snd_sof_load_topology’:
sound/soc/sof/topology.c:2711:27: warning: variable ‘hdr’ set but not used [-Wunused-but-set-variable]
  struct snd_soc_tplg_hdr *hdr;
                           ^~~
  CC [M]  sound/soc/sof/control.o
  CC [M]  sound/soc/sof/trace.o
  CC [M]  sound/soc/sof/utils.o
  CC [M]  sound/soc/sof/compressed.o
  LD [M]  sound/soc/sof/snd-sof.o
  CC [M]  sound/soc/sof/nocodec.o
  LD [M]  sound/soc/sof/snd-sof-nocodec.o
  CC [M]  sound/soc/sof/sof-acpi-dev.o
  CC [M]  sound/soc/sof/sof-pci-dev.o
  CC [M]  sound/soc/sof/sof-spi-dev.o
sound/soc/sof/sof-spi-dev.c:25:32: warning: ‘spi_pm’ defined but not used [-Wunused-const-variable=]
 static const struct dev_pm_ops spi_pm = {
                                ^~~~~~
  CC [M]  sound/soc/sof/hw-spi.o
sound/soc/sof/hw-spi.c: In function ‘spi_irq_handler’:
sound/soc/sof/hw-spi.c:161:22: warning: comparison of unsigned expression >= 0 is always true [-Wtype-limits]
  if (sof_pdata->gpio >= 0 &&
                      ^~
  LD [M]  sound/soc/sof/snd-sof-spi.o
  Building modules, stage 2.
  MODPOST 12 modules
  CC      sound/soc/sof/intel/snd-sof-intel-bdw.mod.o
  LD [M]  sound/soc/sof/intel/snd-sof-intel-bdw.ko
  CC      sound/soc/sof/intel/snd-sof-intel-byt.mod.o
  LD [M]  sound/soc/sof/intel/snd-sof-intel-byt.ko
  CC      sound/soc/sof/intel/snd-sof-intel-hda-common.mod.o
  LD [M]  sound/soc/sof/intel/snd-sof-intel-hda-common.ko
  CC      sound/soc/sof/intel/snd-sof-intel-hda.mod.o
  LD [M]  sound/soc/sof/intel/snd-sof-intel-hda.ko
  CC      sound/soc/sof/intel/snd-sof-intel-hsw.mod.o
  LD [M]  sound/soc/sof/intel/snd-sof-intel-hsw.ko
  CC      sound/soc/sof/snd-sof-nocodec.mod.o
  LD [M]  sound/soc/sof/snd-sof-nocodec.ko
  CC      sound/soc/sof/snd-sof-spi.mod.o
  LD [M]  sound/soc/sof/snd-sof-spi.ko
  CC      sound/soc/sof/snd-sof.mod.o
  LD [M]  sound/soc/sof/snd-sof.ko
  CC      sound/soc/sof/sof-acpi-dev.mod.o
  LD [M]  sound/soc/sof/sof-acpi-dev.ko
  CC      sound/soc/sof/sof-pci-dev.mod.o
  LD [M]  sound/soc/sof/sof-pci-dev.ko
  CC      sound/soc/sof/sof-spi-dev.mod.o
  LD [M]  sound/soc/sof/sof-spi-dev.ko
  CC      sound/soc/sof/xtensa/snd-sof-xtensa-dsp.mod.o
  LD [M]  sound/soc/sof/xtensa/snd-sof-xtensa-dsp.ko