scsi: bnx2fc: Simplify CPU hotplug code

The CPU hotplug related code of this driver can be simplified by:

1) Consolidating the callbacks into a single state. The CPU thread can be
   torn down on the CPU which goes offline. There is no point in delaying
   that to the CPU dead state

2) Let the core code invoke the online/offline callbacks and remove the
   extra for_each_online_cpu() loops.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>