freedreno/a6xx: Fix valid_format_cast logic for newer a6xx
Fixes a pile of dEQP-GLES31.functional.copy_image.non_compressed.viewclass_32_bits.* on a6xx gen2 and later.
Fixes: 87978c39 ("freedreno/a6xx: Allow z24s8 format casts") Signed-off-by: Rob Clark robdclark@chromium.org