drm: add DRM_INFO_ONCE() to print a one-time DRM_INFO() message

Just like DRM_INFO(), but only do it once.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Dave Airlie <airlied@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index 04086c5..04a7f31 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -199,6 +199,9 @@
 #define DRM_INFO(fmt, ...)				\
 	printk(KERN_INFO "[" DRM_NAME "] " fmt, ##__VA_ARGS__)
 
+#define DRM_INFO_ONCE(fmt, ...)				\
+	printk_once(KERN_INFO "[" DRM_NAME "] " fmt, ##__VA_ARGS__)
+
 /**
  * Debug output.
  *