broadcom/vc5: Add lowering for txf_ms to a txf on a 2x2-scaled texture.

The HW has no native sampler support for multisample textures, but since
we only need to support txf_ms and the layout is UIF, we just need to
scale up the texcoords and then add in the sample.

This drops the old TEXTURE_MSAA_ADDR special uniform, since we're treating
MSAA textures as textures, rather than basically texbos like VC4 had to.

src/broadcom/compiler/v3d_compiler.h

@@ -229,8 +229,6 @@ enum quniform_contents {
         QUNIFORM_TEXTURE_ARRAY_SIZE,
         QUNIFORM_TEXTURE_LEVELS,
 
-        QUNIFORM_TEXTURE_MSAA_ADDR,
-
         QUNIFORM_UBO_ADDR,
 
         QUNIFORM_TEXRECT_SCALE_X,