[SCSI] mpt fusion: Firmware event implementation using seperate WorkQueue

Now Firmware events are handled by firmware event queue.
Previously it was handled in interrupt context/WorkQueue of Linux.
Firmware Event handling is restructured and optimized.

Signed-off-by: Kashyap Desai <kadesai@lsi.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>