drm: expose subpixel order name routine v3

Just like we have for connector type etc.

v2: drop static array (Chris)
v3: add kdoc (Daniel)

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Acked-by: Dave Airlie <airlied@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index 71727b6..ce9ee60 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -991,6 +991,7 @@
 
 extern const char *drm_get_connector_name(const struct drm_connector *connector);
 extern const char *drm_get_connector_status_name(enum drm_connector_status status);
+extern const char *drm_get_subpixel_order_name(enum subpixel_order order);
 extern const char *drm_get_dpms_name(int val);
 extern const char *drm_get_dvi_i_subconnector_name(int val);
 extern const char *drm_get_dvi_i_select_name(int val);