drm: include kernel list header file in hashtab header

Signed-off-by: Dave Airlie <airlied@redhat.com>

include/drm/drm_hashtab.h

@@ -35,6 +35,8 @@
 #ifndef DRM_HASHTAB_H
 #define DRM_HASHTAB_H
 
+#include <linux/list.h>
+
 #define drm_hash_entry(_ptr, _type, _member) container_of(_ptr, _type, _member)
 
 struct drm_hash_item {