drm: Extract drm_debugfs.h

Doc polish will follow in the next patch.

v2: Put the include guard #endif at the end (Ville).

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20170322205336.24549-1-daniel.vetter@ffwll.ch
diff --git a/drivers/gpu/drm/drm_debugfs.c b/drivers/gpu/drm/drm_debugfs.c
index 1d2d18d..4b02f42 100644
--- a/drivers/gpu/drm/drm_debugfs.c
+++ b/drivers/gpu/drm/drm_debugfs.c
@@ -34,9 +34,12 @@
 #include <linux/seq_file.h>
 #include <linux/slab.h>
 #include <linux/export.h>
-#include <drm/drmP.h>
+
+#include <drm/drm_debugfs.h>
 #include <drm/drm_edid.h>
 #include <drm/drm_atomic.h>
+#include <drm/drmP.h>
+
 #include "drm_internal.h"
 #include "drm_crtc_internal.h"