sof: coherent: Don't mark "struct coherent" as packed #15715

Job	Run time
build-linux (mnfst, imx8 imx8x imx8m)	4m 12s
build-linux (mnfst, mtl)	4m 12s
build-windows (imx8 imx8x imx8m)	6m 7s
build-linux (mnfst, lnl)	4m 13s
build-windows (mtl)	5m 24s
build-linux (mnfst, tgl tgl-h)	4m 58s
build-windows (tgl tgl-h)	6m 54s
LP64-WIP	3m 22s
build-linux (zmain, imx8 imx8x imx8m)	4m 5s
build-windows (-d, mtl)	6m 6s
manifest-check	40s
build-linux (zmain, mtl)	4m 20s
build-linux (zmain, lnl)	3m 45s
build-linux (zmain, tgl tgl-h)	4m 50s
build-linux (-d, mnfst, mtl)	4m 23s
compare-linux-win	33s
	1h 8m 4s

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