bnx2x: Fix no link on 577xx 10G-baseT

Since the Warpcore supports various link types, need to set only the correct
supported modes for XFI which is the serdes interface for the 10G-baseT PHY.

Signed-off-by: Yaniv Rosner <yanivr@broadcom.com>
Signed-off-by: Barak Witkowski <barak@broadcom.com>
Signed-off-by: Dmitry Kravkov <dmitry@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>