radeonsi/vcn: fix regression in yuv422 jpeg decode

radeonsi/vcn: fix regression in yuv422 jpeg decode

- yuv422 decode was blocked in 12acee17fad5, enable it back.
- nv12 yuv422 and grayscale decode is supported on all versions.
- JPEG2 and higher versions supports 444p decode.
- add l8_unorm to supported formats, can be used for grayscale.

Fixes: 12acee17fad5 (frontends/va: reallocate surface for yuv400/yuv444 picture)

v2: indent the switch case correctly (Thong Thai)

Signed-off-by: Sathishkumar S <sathishkumar.sundararaju@amd.com>
Reviewed-by: Thong Thai <thong.thai@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20165>