drm: Hide hw.lock cleanup in filp->release better

A few things:
- Rename the cleanup function from drm_master_release to
  drm_legacy_lock_release. It doesn't relase any master stuff, but
  just the legacy hw lock.
- Hide it in drm_lock.c, which allows us to make a few more functions
  static in there. To avoid forward decl we need to shuffle the code a
  bit though.
- Push the check for ->master into the function itself.
- Only call this for !DRIVER_MODESET.

End result: Another place that takes struct_mutex gone for good for
modern drivers.

v2: Remove leftover comment.

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1465930269-7883-3-git-send-email-daniel.vetter@ffwll.ch

drivers/gpu/drm/drm_legacy.h

@@ -88,14 +88,10 @@ struct drm_agp_mem {
 	struct list_head head;
 };
 
-/*
- * Generic Userspace Locking-API
- */
-
-int drm_legacy_i_have_hw_lock(struct drm_device *d, struct drm_file *f);
+/* drm_lock.c */
 int drm_legacy_lock(struct drm_device *d, void *v, struct drm_file *f);
 int drm_legacy_unlock(struct drm_device *d, void *v, struct drm_file *f);
-int drm_legacy_lock_free(struct drm_lock_data *lock, unsigned int ctx);
+void drm_legacy_lock_release(struct drm_device *dev, struct file *filp);
 
 /* DMA support */
 int drm_legacy_dma_setup(struct drm_device *dev);