qed: Add RoCE ll2 & GSI support

Add the RoCE-specific LL2 logic [as well as GSI support] over
the 'generic' LL2 interface.

Signed-off-by: Ram Amrani <Ram.Amrani@caviumnetworks.com>
Signed-off-by: Yuval Mintz <Yuval.Mintz@caviumnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>