vc4: Mark texturing setup instructions as having side effects.
vc4: Mark texturing setup instructions as having side effects.

We need to not DCE them even though they don't have a destination in QIR.
We also shouldn't relocate them in vc4_opt_vpm.  Neither of these things
happen, but I'm about to make DCE consider instructions with a NULL
destination.

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler