cciss: kernel scan thread for MSA2012

The MSA2012 cannot inform the driver of configuration changes since all
management is out of band.  This is a departure from any storage we have
supported in the past.  We need some way to detect changes on the topology
so we implement this kernel thread.  In some instances there's nothing we
can do from the driver (like LUN failure) so just print out a message.  In
the case where logical volumes are added or deleted we call
rebuild_lun_table to refresh the driver's view of the world.

Signed-off-by: Mike Miller <mike.miller@hp.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>