nir: Add nir_lower_tex support for Broadcom's swizzled TG4 results.

V3D returns the texels in a different order in the resulting vec4 from
what GLSL wants, so we need to put in a swizzle.  Fixes
dEQP-GLES31.functional.texture.gather.basic.2d.rgba8.base_level.level_1

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
3 files changed