qla2xxx: Add framework for async fabric discovery

Currently code performs a full scan of the fabric for
every RSCN. Its an expensive process in a noisy large SAN.

This patch optimizes expensive fabric discovery process by
scanning switch for the affected port when RSCN is received.

Currently Initiator Mode code makes login/logout decision without
knowledge of target mode. This causes driver and firmware to go
out-of-sync. This framework synchronizes both initiator mode
personality and target mode personality in making login/logout
decision.

This patch adds following capabilities in the driver

- Send Notification Acknowledgement asynchronously.
- Update session/fcport state asynchronously.
- Create a session or fcport struct asynchronously.
- Send GNL asynchronously. The command will ask FW to
  provide a list of FC Port entries FW knows about.
- Send GPDB asynchronously. The command will ask FW to
  provide detail data of an FC Port FW knows about or
  perform ADISC to verify the state of the session.
- Send GPNID asynchronously. The command will ask switch
  to provide WWPN for provided NPort ID.
- Send GPSC asynchronously. The command will ask switch
  to provide registered port speed for provided WWPN.
- Send GIDPN asynchronously. The command will ask the
  switch to provide Nport ID for provided WWPN.
- In driver unload path, schedule all session for deletion
  and wait for deletion to complete before allowing driver
  unload to proceed.

Signed-off-by: Quinn Tran <quinn.tran@cavium.com>
Signed-off-by: Himanshu Madhani <himanshu.madhani@cavium.com>
[ bvanassche: fixed spelling in patch description ]
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>