Add support for the 10G-baseT PHY - BCM84834, which is the quad-port version of
the dual-port BCM84833.

Signed-off-by: Yaniv Rosner <yanivr@broadcom.com>
Signed-off-by: Eilon Greenstein <eilong@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>