radv/ac: refactor our fmask sample index fixup.
radv/ac: refactor our fmask sample index fixup.

This refactors out the sample index fixup between
txf and image load.

Reviewed-by: Bas Nieuwenhuizen <1d31d94f30d40df7951505d1034e1e923d02ec49@basnieuwenhuizen.nl>
Signed-off-by: Dave Airlie <f2295d84e358395675bc8031be58672073ae065e@redhat.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler