xircom: remove redundant error check on variable err

The error check on err is always false as err is always 0 at the
port_found label. The code is redundant and can be removed.

Addresses-Coverity: ("Logically dead code")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>