drm/bochs: Use the drm_driver.dumb_destroy default

drm_gem_dumb_destroy() is the drm_driver.dumb_destroy default,
so no need to set it.

Cc: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/1502034068-51384-17-git-send-email-noralf@tronnes.org

drivers/gpu/drm/bochs/bochs_drv.c

@@ -93,7 +93,6 @@ static struct drm_driver bochs_driver = {
 	.gem_free_object_unlocked = bochs_gem_free_object,
 	.dumb_create            = bochs_dumb_create,
 	.dumb_map_offset        = bochs_dumb_mmap_offset,
-	.dumb_destroy           = drm_gem_dumb_destroy,
 };
 
 /* ---------------------------------------------------------------------- */