vc4: Store reloc pointers as pointers, not offsets.
vc4: Store reloc pointers as pointers, not offsets.

Now that we don't resize the CL as we build (it's set up at the top by
vc4_start_draw()), we can store the pointers instead of offsets from
the base.  Saves a bit of math in emitting relocs (about 60 bytes of
code).

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler