[SCSI] bfa: Introduce a link notification state machine.

Introduce a link notification state machine to handle next incoming
link events while the current event is being delivered to the driver.

When the event has been processed by the driver, the link notification
state machine will queue the next event (if there is any) to the
driver.

Signed-off-by: Krishna Gudipati <kgudipat@brocade.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>