i965/gs: Add a state atom to set up geometry shader state.

i965/gs: Add a state atom to set up geometry shader state.

v2: Do not attempt to share the code that uploads
3DSTATE_BINDING_TABLE_POINTERS_GS, 3DSTATE_SAMPLER_STATE_POINTERS_GS,
or 3DSTATE_GS with VS.

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
v3: Add _NEW_TRANSFORM to gen7_gs_state.

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