drm/i915: Bail out early on gen6_signal if no semaphores

If we dont have semaphores enabled, we allocate 4
dwords for signalling. But end up emitting more regardless.

Fix this by bailing out early if semaphores are not enabled.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=78274
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=78283
Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_ringbuffer.c

@@ -684,6 +684,8 @@ static int gen6_signal(struct intel_ring_buffer *signaller,
 #define MBOX_UPDATE_DWORDS 4
 	if (i915_semaphore_is_enabled(dev))
 		num_dwords += ((I915_NUM_RINGS-1) * MBOX_UPDATE_DWORDS);
+	else
+		return intel_ring_begin(signaller, num_dwords);
 
 	ret = intel_ring_begin(signaller, num_dwords);
 	if (ret)