i965/fs: Split VGRFs after lowering pull constants
The split_virtual_grfs code doesn't properly rewrite reladdr so we need to make sure that any uniform indirects are lowered away first. This fixes the glsl-fs-uniform-indexed-by-swizzled-vec4.shader_test in piglit Cc: "10.6" <mesa-stable@lists.freedesktop.org> Reviewed-by:Kenneth Graunke <kenneth@whitecape.org> (cherry picked from commit fee0c5af)