zephyr: add rtos/mutex.h #666

Job	Run time
LP64-WIP	3m 48s
build-windows (imx8 imx8x imx8m imx8ulp)	8m 46s
build-linux (mnfst, imx8 imx8x imx8m imx8ulp)	5m 46s
build-windows (mtl)	7m 11s
build-linux (mnfst, mtl)	4m 14s
build-windows (tgl tgl-h)	8m 14s
manifest-check	47s
build-linux (mnfst, lnl)	4m 4s
build-windows (-d, mtl)	7m 26s
build-linux (mnfst, tgl tgl-h)	5m 26s
build-linux (zmain, imx8 imx8x imx8m imx8ulp)	6m 6s
build-linux (zmain, mtl)	4m 40s
build-linux (zmain, lnl)	4m 14s
build-linux (zmain, tgl tgl-h)	5m 6s
build-linux (-d, mnfst, mtl)	4m 40s
build-linux (mnfst, --all)	10m 12s
compare-linux-win	31s
	1h 31m 11s

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