vc4: When asked to sample from a raster texture, make a shadow tiled copy.

vc4: When asked to sample from a raster texture, make a shadow tiled copy.

So, it turns out my simulator doesn't *quite* match the hardware.  And the
errata about raster textures tells you most of what's wrong, but there's
still stuff wrong after that.  Instead, if we're asked to sample from
raster, we'll just blit it to a tiled temporary.

Raster textures should only be screen scanout, and word is that it's
faster to copy to tiled using the tiling engine first than to texture from
an entire raster texture, anyway.