qed: Add link support

Physical link is handled by the management Firmware.
This patch lays the infrastructure for attention handling in the driver,
as link change notifications arrive via async. attentions,
as well the handling of such notifications.

This patch also extends the API with the protocol drivers by adding
registered callbacks which the protocol driver passes to qed in order
to be notified of async. events originating from the FW/HW.

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>