drm: use memdup_user() as a cleanup

drivers/gpu/drm/r128/r128_state.c:1014:10-17: WARNING opportunity for memdup_user
/c/kernel-tests/src/cocci/drivers/gpu/drm/r128/r128_state.c:1029:9-16: WARNING opportunity for memdup_user
/c/kernel-tests/src/cocci/drivers/gpu/drm/r128/r128_state.c:904:10-17: WARNING opportunity for memdup_user
/c/kernel-tests/src/cocci/drivers/gpu/drm/r128/r128_state.c:914:9-16: WARNING opportunity for memdup_user

 Use memdup_user rather than duplicating its implementation
 This is a little bit restricted to reduce false positives

Generated by: coccinelle/api/memdup_user.cocci

CC: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>