drm/arc: Use .dumb_map_offset and .dumb_destroy defaults

This driver can use the drm_driver.dumb_destroy and
drm_driver.dumb_map_offset defaults, so no need to set them.

Cc: Alexey Brodkin <abrodkin@synopsys.com>
Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Acked-by: Alexey Brodkin <abrodkin@synopsys.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1500837417-40580-4-git-send-email-noralf@tronnes.org

drivers/gpu/drm/arc/arcpgu_drv.c

@@ -172,8 +172,6 @@ static struct drm_driver arcpgu_drm_driver = {
 	.patchlevel = 0,
 	.fops = &arcpgu_drm_ops,
 	.dumb_create = drm_gem_cma_dumb_create,
-	.dumb_map_offset = drm_gem_cma_dumb_map_offset,
-	.dumb_destroy = drm_gem_dumb_destroy,
 	.prime_handle_to_fd = drm_gem_prime_handle_to_fd,
 	.prime_fd_to_handle = drm_gem_prime_fd_to_handle,
 	.gem_free_object_unlocked = drm_gem_cma_free_object,