vc4: Add support for TGSI_OPCODE_UCMP.
vc4: Add support for TGSI_OPCODE_UCMP.

This is being emitted now from st_glsl_to_tgsi.cpp.

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler