qed: Add support for query/config dcbx.

Query API reads the dcbx data from the device shared memory and return it
to the caller. The config API configures the user provided dcbx values on
the device, and initiates the dcbx negotiation with the peer.

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