[SCSI] mpt2sas: fix hotplug event processing

Here's a fix for hotplug events.  The useage of queue_delayed_work seems
to broke the fifo for processing of firmware events.  After several iterations
of adding and removing cabling connected to jbods, the devices are not
getting added becuase kernel thread is activited out of order.

Signed-off-by: Eric Moore <eric.moore@lsi.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>