ipc4: replace fw_reg spinlock with mutex #22872

Job	Run time
manifest-check	2m 43s
LP64-WIP	3m 53s
build-windows (mnfst, tgl)	8m 37s
build-windows (mnfst, imx8 imx8x)	10m 43s
build-windows (mnfst, ptl)	9m 28s
build-windows (mnfst, imx8m imx8ulp)	9m 49s
build-windows (mnfst, lnl)	8m 18s
build-windows (mnfst, tgl-h)	7m 49s
build-windows (-d, mnfst, lnl)	9m 16s
build-linux (mnfst, tgl-h)	3m 57s
build-linux (mnfst, wcl imx95)	7m 3s
build-windows (mnfst, mtl)	9m 3s
build-linux (mnfst, ptl)	5m 55s
build-linux (mnfst, imx8m imx8ulp)	4m 45s
build-linux (mnfst, lnl)	4m 15s
build-linux (-d, mnfst, lnl)	4m 24s
build-linux (mnfst, tgl)	4m 53s
build-linux (mnfst, mtl)	4m 21s
build-linux (mnfst, imx8 imx8x)	5m 31s
compare-linux-win	28s
	2h 5m 11s

Provide feedback