We were leaving an undefined value since the ralloc zeroing changes.
Fixes nir_validate() failures on vc4.
v2: Fix the color-index case of drawpixels as well.
Reviewed-by: Rob Clark <robdclark@gmail.com> (v1)
Generally you'd see the gl_Color reference first and get some cursor set.
However, in piglit draw-pixel-with-texture we're now seeing the TexCoord
dereferenced first.
Reviewed-by: Rob Clark <robdclark@gmail.com>
