kpb: calculate free space in history buffer - #2343

kpb: calculate free space in history buffer#2343

bkokoszx wants to merge 3 commits into

thesofproject:masterthesofproject/sof:masterfrom

bkokoszx:fix-kpb-draining-issuebkokoszx/sof:fix-kpb-draining-issueCopy head branch name to clipboard