vc4: Fix render target NPOT alignment at small miplevels.
vc4: Fix render target NPOT alignment at small miplevels.

The texturing hardware takes the POT level 0 width/height and minifies
those.  This is different from what we were doing, for example, for
273-wide's level 5: POT(273>>5) == 8, while POT(273)>>5 == 16.

Fixes piglit-depthstencil-render-miplevels 273.

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler