fix realtek phy id in forcedeth

As noticed by Chuck Ebbert, commit c5e3ae88
introduced a copy-paste typo, as realtek phy is 0x732 and not 0x1c1. Obvious
fix below suggested by Ayaz Abdulla.

Signed-off-by: Willy Tarreau <w@1wt.eu>
Cc: Ayaz Abdulla <aabdulla@nvidia.com>
Cc: Chuck Ebbert <cebbert@redhat.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>