rimage: Remove up-down-mixer from mtl.toml #198

Job	Run time
manifest-check	50s
LP64-WIP	4m 12s
build-windows (imx8 imx8x imx8m)	2m 56s
build-linux (mnfst, imx8 imx8x imx8m)	50s
build-windows (tgl tgl-h)	3m 5s
build-linux (mnfst, tgl tgl-h)	40s
build-windows (mtl)	4m 56s
build-linux (mnfst, mtl)	1m 1s
build-windows (-i IPC4 tgl tgl-h)	3m 5s
build-linux (mnfst, lnl)	43s
build-windows (-d, mtl)	3m 11s
build-linux (mnfst, -i IPC4 tgl tgl-h)	45s
build-linux (zmain, imx8 imx8x imx8m)	57s
build-linux (zmain, tgl tgl-h)	1m 1s
build-linux (zmain, mtl)	1m 0s
build-linux (zmain, lnl)	1m 0s
build-linux (zmain, -i IPC4 tgl tgl-h)	47s
build-linux (-d, mnfst, mtl)	57s
compare-linux-win	22s
	32m 18s

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