tg3: Add 5717 serdes phy ID

The serdes and copper phys of the 5717 asic rev have different phy IDs.
This patch adds the serdes phy ID.

Signed-off-by: Matt Carlson <mcarlson@broadcom.com>
Reviewed-by: Michael Chan <mchan@broadcom.com>
Reviewed-by: Benjamin Li <benli@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>