We should unlock here before returning -EINVAL.

Fixes: 39ad4600 ('dmaengine: s3c24xx: Split device_control')
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Acked-by: NMaxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: NVinod Koul <vinod.koul@intel.com>