st/mesa: don't check st->vp in update_clip
st/mesa: don't check st->vp in update_clip

The clip state is updated before VS, so it can be NULL for the first draw
call. Just remove the unnecessary dependency on st->vp.

Reviewed-by: Brian Paul <3cb4e1df5ec4da2c7c4af7c52cec8cf340a55a10@vmware.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler