drm/i915/fbc: Move flip_pending assignmnt

Move the flip_pending assignment into __intel_fbc_post_update()
from intel_fbc_post_update(). Now mirrors the pre_update() side.

The only reason the assignment was in the higher level function
is that we used to call __intel_fbc_post_update() from elsewhere
as well. That got cleaned up in commit b39d2c62 ("drm/i915/fbc:
Call intel_fbc_activate() directly from frontbuffer flush")
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220620182917.10765-1-ville.syrjala@linux.intel.comReviewed-by: Mika Kahola <mika.kahola@intel.com>

drivers/gpu/drm/i915/display/intel_fbc.c

@@ -1303,6 +1303,8 @@ static void __intel_fbc_post_update(struct intel_fbc *fbc)
 
 	drm_WARN_ON(&i915->drm, !mutex_is_locked(&fbc->lock));
 
+	fbc->flip_pending = false;
+
 	if (!fbc->busy_bits)
 		intel_fbc_activate(fbc);
 	else
@@ -1324,10 +1326,8 @@ void intel_fbc_post_update(struct intel_atomic_state *state,
 
 		mutex_lock(&fbc->lock);
 
-		if (fbc->state.plane == plane) {
-			fbc->flip_pending = false;
+		if (fbc->state.plane == plane)
 			__intel_fbc_post_update(fbc);
-		}
 
 		mutex_unlock(&fbc->lock);
 	}