qed: Add support for Energy efficient ethernet.

The patch adds required driver support for reading/configuring the
Energy Efficient Ethernet (EEE) parameters.

Signed-off-by: Sudarsana Reddy Kalluru <sudarsana.kalluru@cavium.com>
Signed-off-by: Yuval Mintz <yuval.mintz@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>