radv/ac: add support for multi sample image coords
radv/ac: add support for multi sample image coords

This just adds the nir->llvm support, enabling
the extension causes some failures on llvm 3.9 at least,
but this code seems fine.

NIR passes the sampler in src[1].x, and we LLVM/SI requires
it as the last parameters in the coords (coord[2] for 2D,
coord[3] for 2DArray).

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

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler