drm/xen: Drop drm_gem_prime_export/import

They're the default.

Aside: Would be really nice to switch the others over to
drm_gem_object_funcs.

Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Cc: xen-devel@lists.xenproject.org
Link: https://patchwork.freedesktop.org/patch/msgid/20190614203615.12639-39-daniel.vetter@ffwll.ch

drivers/gpu/drm/xen/xen_drm_front.c

@@ -491,8 +491,6 @@ static struct drm_driver xen_drm_driver = {
 	.gem_free_object_unlocked  = xen_drm_drv_free_object_unlocked,
 	.prime_handle_to_fd        = drm_gem_prime_handle_to_fd,
 	.prime_fd_to_handle        = drm_gem_prime_fd_to_handle,
-	.gem_prime_import          = drm_gem_prime_import,
-	.gem_prime_export          = drm_gem_prime_export,
 	.gem_prime_import_sg_table = xen_drm_front_gem_import_sg_table,
 	.gem_prime_get_sg_table    = xen_drm_front_gem_get_sg_table,
 	.gem_prime_vmap            = xen_drm_front_gem_prime_vmap,