anv: Handle dwords that are all MBZ correctly
anv: Handle dwords that are all MBZ correctly

A few packets have dwords in them that are all MBZ and we failed to
write those. This change makes sure we iterate through all dwords and
write them all.

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler