i965/gen7+: Move sampler state packets to the stage sampler state table update.

i965/gen7+: Move sampler state packets to the stage sampler state table update.

Now that we have the stage state coming into our setup of sampler states,
it's easy to drop an identifier into it of which stage the stage_state is,
and then look up which packet to emit in a little table.

No performance difference on cairo on glamor (n=492).

v2: Don't forget to do the workaround flush on IVB.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>