qed: Add slowpath L2 support

This patch adds to the qed the support to configure various L2 elements,
such as channels and basic filtering conditions.
It also enhances its public API to allow qede to later utilize this
functionality.

Signed-off-by: Manish Chopra <Manish.Chopra@qlogic.com>
Signed-off-by: Yuval Mintz <Yuval.Mintz@qlogic.com>
Signed-off-by: Ariel Elior <Ariel.Elior@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>