au0828_v4l2_device_register() unlocks au0828_dev->lock and frees au0828
dev in error legs before return. au0828_usb_probe() does the same when
au0828_v4l2_device_register() returns error.

Fix au0828_v4l2_device_register() to not to unlock and free in its error
legs.
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>