i965: Unify CC_STATE and BLEND_STATE atoms on Haswell as a workaround

i965: Unify CC_STATE and BLEND_STATE atoms on Haswell as a workaround

Re-emitting 3DSTATE_CC_STATE_POINTERS after emitting
3DSTATE_BLEND_STATE_POINTERS fixes the shadow flickering in
SuperTuxCart and Tropico 6 which was seen only on Haswell.
The reason for this is unknown and fix was found empirically.

The closest mention in PRM is that it should improve performance.
From the HSW PRM, volume 2b, page 823 (3DSTATE_BLEND_STATE_POINTERS):
 "When the BLEND_STATE pointer changes but not the CC_STATE pointer,
  driver needs to force a CC_STATE pointer change to improve
  blend performance in pixel backend."

Closes: https://gitlab.freedesktop.org/mesa/mesa/issues/1834
Fixes: eca4a654 ("i965: Disable dual source blending when shader doesn't support it on gen8+")
Cc: <mesa-stable@lists.freedesktop.org>
Signed-off-by: Danylo Piliaiev <danylo.piliaiev@globallogic.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>