drm: drop extern from function decls

It's the default storage class for functions, entirely redundant. And
a lot of these headers are a bit inconsistent due to organically
grown.

Reviewed-by: Gabriel Krisman Bertazi <krisman@collabora.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20170322083617.13361-2-daniel.vetter@ffwll.ch
diff --git a/include/drm/drm_hashtab.h b/include/drm/drm_hashtab.h
index fce2ef3..bb95ff0 100644
--- a/include/drm/drm_hashtab.h
+++ b/include/drm/drm_hashtab.h
@@ -49,17 +49,17 @@
 	u8 order;
 };
 
-extern int drm_ht_create(struct drm_open_hash *ht, unsigned int order);
-extern int drm_ht_insert_item(struct drm_open_hash *ht, struct drm_hash_item *item);
-extern int drm_ht_just_insert_please(struct drm_open_hash *ht, struct drm_hash_item *item,
-				     unsigned long seed, int bits, int shift,
-				     unsigned long add);
-extern int drm_ht_find_item(struct drm_open_hash *ht, unsigned long key, struct drm_hash_item **item);
+int drm_ht_create(struct drm_open_hash *ht, unsigned int order);
+int drm_ht_insert_item(struct drm_open_hash *ht, struct drm_hash_item *item);
+int drm_ht_just_insert_please(struct drm_open_hash *ht, struct drm_hash_item *item,
+			      unsigned long seed, int bits, int shift,
+			      unsigned long add);
+int drm_ht_find_item(struct drm_open_hash *ht, unsigned long key, struct drm_hash_item **item);
 
-extern void drm_ht_verbose_list(struct drm_open_hash *ht, unsigned long key);
-extern int drm_ht_remove_key(struct drm_open_hash *ht, unsigned long key);
-extern int drm_ht_remove_item(struct drm_open_hash *ht, struct drm_hash_item *item);
-extern void drm_ht_remove(struct drm_open_hash *ht);
+void drm_ht_verbose_list(struct drm_open_hash *ht, unsigned long key);
+int drm_ht_remove_key(struct drm_open_hash *ht, unsigned long key);
+int drm_ht_remove_item(struct drm_open_hash *ht, struct drm_hash_item *item);
+void drm_ht_remove(struct drm_open_hash *ht);
 
 /*
  * RCU-safe interface