drivers: gpu: Mark functions as static in vmwgfx_fence.c

Mark functions as static because they are not used outside the file
drm/vmwgfx/vmwgfx_fence.c.

This eliminates the following warnings in drm/vmwgfx/vmwgfx_fence.c:
drivers/gpu/drm/vmwgfx/vmwgfx_fence.c:274:6: warning: no previous prototype for ‘vmw_fences_perform_actions’ [-Wmissing-prototypes]
drivers/gpu/drm/vmwgfx/vmwgfx_fence.c:900:6: warning: no previous prototype for ‘vmw_fence_obj_add_action’ [-Wmissing-prototypes]
drivers/gpu/drm/vmwgfx/vmwgfx_fence.c:996:5: warning: no previous prototype for ‘vmw_event_fence_action_create’ [-Wmissing-prototypes]

Signed-off-by: Rashika Kheria <rashika.kheria@gmail.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Reviewed-by: Jakob Bornecrantz <jakob@vmware.com>

drivers/gpu/drm/vmwgfx/vmwgfx_fence.c

@@ -271,7 +271,7 @@ void vmw_fence_obj_unreference(struct vmw_fence_obj **fence_p)
 	spin_unlock_irq(&fman->lock);
 }
 
-void vmw_fences_perform_actions(struct vmw_fence_manager *fman,
+static void vmw_fences_perform_actions(struct vmw_fence_manager *fman,
 				struct list_head *list)
 {
 	struct vmw_fence_action *action, *next_action;
@@ -897,7 +897,7 @@ static void vmw_event_fence_action_cleanup(struct vmw_fence_action *action)
  * Note that the action callbacks may be executed before this function
  * returns.
  */
-void vmw_fence_obj_add_action(struct vmw_fence_obj *fence,
+static void vmw_fence_obj_add_action(struct vmw_fence_obj *fence,
 			      struct vmw_fence_action *action)
 {
 	struct vmw_fence_manager *fman = fence->fman;
@@ -993,7 +993,7 @@ struct vmw_event_fence_pending {
 	struct drm_vmw_event_fence event;
 };
 
-int vmw_event_fence_action_create(struct drm_file *file_priv,
+static int vmw_event_fence_action_create(struct drm_file *file_priv,
 				  struct vmw_fence_obj *fence,
 				  uint32_t flags,
 				  uint64_t user_data,