scsi: bnx2fc: Plug CPU hotplug race

bnx2fc_process_new_cqes() has protection against CPU hotplug, which relies
on the per cpu thread pointer. This protection is racy because it happens
only partially with the per cpu fp_work_lock held.

If the CPU is unplugged after the lock is dropped, the wakeup code can
dereference a NULL pointer or access freed and potentially reused memory.

Restructure the code so the thread check and wakeup happens with the
fp_work_lock held.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Chad Dupuis <chad.dupuis@cavium.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>