ubi: Do not drop UBI device reference before using

The UBI device reference is dropped but then the device is used as a
parameter of ubi_err. The bug is introduced in changing ubi_err's
behavior. The old ubi_err does not require a UBI device as its first
parameter, but the new one does.

Fixes: 32608703 ("UBI: Extend UBI layer debug/messaging capabilities")
Signed-off-by: Pan Bian <bianpan2016@163.com>
Reviewed-by: Boris Brezillon <boris.brezillon@bootlin.com>
Signed-off-by: Richard Weinberger <richard@nod.at>