drm: add proper return value for drm_mode_crtc_set_gamma_size

drm_mode_crtc_set_gamma_size returns boolean true for success
and false for failure. This is not very kernel conform, so
change it to return 0 for success and a propert error code
otherwise. Noone checks the return value, so no users have to
be fixed.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index 33ebe29..df6e413 100644
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -3024,7 +3024,7 @@
 }
 EXPORT_SYMBOL(drm_mode_connector_detach_encoder);
 
-bool drm_mode_crtc_set_gamma_size(struct drm_crtc *crtc,
+int drm_mode_crtc_set_gamma_size(struct drm_crtc *crtc,
 				  int gamma_size)
 {
 	crtc->gamma_size = gamma_size;
@@ -3032,10 +3032,10 @@
 	crtc->gamma_store = kzalloc(gamma_size * sizeof(uint16_t) * 3, GFP_KERNEL);
 	if (!crtc->gamma_store) {
 		crtc->gamma_size = 0;
-		return false;
+		return -ENOMEM;
 	}
 
-	return true;
+	return 0;
 }
 EXPORT_SYMBOL(drm_mode_crtc_set_gamma_size);