vc4: Fix miscalculation of the VPM space.
vc4: Fix miscalculation of the VPM space.

We pass in a byte offset, not dword.  I'm rather scared that this actually
managed to pass piglit, but it does fix gears.

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler