[SCSI] qla2xxx: Add FC-transport Asynchronous Event Notification support.

Supported events include LIP, LIP reset, RSCN, link up, and link
down.

To support AEN (and additional forthcoming features), we also
introduce a simple deferred-work construct to manage events which
require a non-atomic sleeping-capable context.  This work-list is
processed as part of the driver's standard DPC routine.

Signed-off-by: Andrew Vasquez <andrew.vasquez@qlogic.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>