drm/i915/fbc: Call intel_fbc_activate() directly from frontbuffer flush

Remove the pointless detour via __intel_fbc_post_update() during
frontbuffer flush.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220315140001.1172-8-ville.syrjala@linux.intel.comReviewed-by: Mika Kahola <mika.kahola@intel.com>

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

@@ -1379,7 +1379,7 @@ static void __intel_fbc_flush(struct intel_fbc *fbc,
 	if (fbc->active)
 		intel_fbc_nuke(fbc);
 	else
-		__intel_fbc_post_update(fbc);
+		intel_fbc_activate(fbc);
 
 out:
 	mutex_unlock(&fbc->lock);