nir: Zero out texture instructions when creating them.
nir: Zero out texture instructions when creating them.

There are so many flags in textures, that the CSE pass would have a hard
time referencing the correct set when figuring out if two texture ops are
the same.  By zeroing, we can avoid that fragility.

Reviewed-by: Jason Ekstrand <b186559eaedf698788888c8a2559b4efb4db10d6@intel.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler