drm/xe/tlb: drop unnecessary smp_wmb()

wake_up_all() and wait_event_timeout() already have the correct barriers
as per https://www.kernel.org/doc/Documentation/memory-barriers.txt.
This should ensure that the seqno_recv write can't be re-ordered wrt to
the actual wake_up_all() i.e we get woken up but there is no write.  The
reader side with wait_event_timeout() also has the correct barriers.
With that drop the hand rolled smp_wmb(), which is anyway missing some
kind of matching barrier on the reader side.
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drivers/gpu/drm/xe/xe_gt_tlb_invalidation.c

@@ -333,8 +333,11 @@ int xe_guc_tlb_invalidation_done_handler(struct xe_guc *guc, u32 *msg, u32 len)
 			expected_seqno, msg[0]);
 	}
 
+	/*
+	 * wake_up_all() and wait_event_timeout() already have the correct
+	 * barriers.
+	 */
 	gt->tlb_invalidation.seqno_recv = msg[0];
-	smp_wmb();
 	wake_up_all(&guc->ct.wq);
 
 	fence = list_first_entry_or_null(&gt->tlb_invalidation.pending_fences,