drm/xe/xelp: Quiesce memory traffic before invalidating AuxCCS

drm/xe/xelp: Quiesce memory traffic before invalidating AuxCCS

According to i915 commit
ad8ebf12217e ("drm/i915/gt: Ensure memory quiesced before invalidation")
quiescing of the memory traffic is required before invalidating the AuxCCS
tables.

Add an extra pipe control flush to achieve that.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patch.msgid.link/20260324084018.20353-5-tvrtko.ursulin@igalia.com
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>