math: fft: move NULL guard before plan dereferences in HiFi3 variants #23130

Job	Run time
LP64-WIP	3m 45s
build-windows (mnfst, imx8 imx8x)	10m 28s
build-windows (mnfst, imx8m imx8ulp)	11m 20s
build-linux (mnfst, imx8 imx8x)	5m 31s
build-windows (mnfst, lnl)	8m 20s
build-windows (mnfst, tgl)	8m 53s
build-linux (-d, mnfst, lnl)	4m 24s
build-linux (mnfst, imx8m imx8ulp)	5m 1s
manifest-check	2m 52s
build-windows (-d, mnfst, lnl)	10m 41s
build-linux (mnfst, tgl-h)	4m 10s
build-windows (mnfst, mtl)	8m 47s
build-linux (mnfst, wcl imx95)	7m 13s
build-linux (mnfst, lnl)	4m 20s
build-linux (mnfst, ptl)	6m 21s
build-windows (mnfst, ptl)	13m 5s
build-linux (mnfst, mtl)	4m 48s
build-windows (mnfst, tgl-h)	9m 35s
build-linux (mnfst, tgl)	4m 33s
compare-linux-win	25s
	2h 14m 32s

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