netxen_nic: set rcode to the return status from the call to netxen_issue_cmd

Currently rcode is being initialized to NX_RCODE_SUCCESS and later it
is checked to see if it is not NX_RCODE_SUCCESS which is never true. It
appears that there is an unintentional missing assignment of rcode from
the return of the call to netxen_issue_cmd() that was dropped in
an earlier fix, so add it in.

Detected by CoverityScan, CID#401900 ("Logically dead code")

Fixes: 2dcd5d95

 ("netxen_nic: fix cdrp race condition")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>