zephyr: alloc: ace: calculate L3 heap size based on actual IMR size #350

Job	Run time
manifest-check	2m 5s
LP64-WIP	2m 4s
build-linux (mnfst, mtl lnl)	2m 4s
build-linux (zmain, imx8 imx8x imx8m imx8ulp)	2m 4s
build-linux (mnfst, imx8 imx8x imx8m imx8ulp)	2m 5s
build-linux (mnfst, tgl tgl-h)	2m 4s
build-linux (mnfst, ptl)	2m 5s
build-linux (zmain, ptl)	2m 4s
build-windows (mtl lnl)	2m 9s
build-windows (tgl tgl-h)	2m 9s
build-linux (zmain, mtl lnl)	2m 5s
build-linux (-d, mnfst, lnl)	2m 4s
build-windows (imx8 imx8x imx8m imx8ulp)	2m 7s
build-linux (zmain, tgl tgl-h)	2m 5s
build-linux (mnfst, --all)	2m 4s
build-windows (ptl)	2m 8s
build-windows (-d, lnl)	2m 7s
compare-linux-win	22s
	35m 55s

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