liquidio: silence a locking static checker warning

Presumably we never hit this return, but static checkers complain that
we need to unlock so we may as well fix that.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Felix Manlunas <felix.manlunas@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>