drm/i915: Return a drm_mode_status enum in the mode_valid vfuncs

We had some mode_valid() vfuncs returning an int, others the enum. Let's
use the latter everywhere.

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_crt.c b/drivers/gpu/drm/i915/intel_crt.c
index b5b1b9b..e2e39e6 100644
--- a/drivers/gpu/drm/i915/intel_crt.c
+++ b/drivers/gpu/drm/i915/intel_crt.c
@@ -222,8 +222,9 @@
 	intel_modeset_check_state(connector->dev);
 }
 
-static int intel_crt_mode_valid(struct drm_connector *connector,
-				struct drm_display_mode *mode)
+static enum drm_mode_status
+intel_crt_mode_valid(struct drm_connector *connector,
+		     struct drm_display_mode *mode)
 {
 	struct drm_device *dev = connector->dev;