cavium/liquidio: fix some error handling in lio_set_phys_id()

There was a missing assignment so the "if (ret)" on the next line is
never true.

Fixes: f21fb3ed ('Add support of Cavium Liquidio ethernet adapters')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>