[SCSI] hpsa: remove scan thread

The intent of the scan thread was to allow a UNIT ATTENTION/LUN
DATA CHANGED condition encountered in the interrupt handler
to trigger a rescan of devices, which can't be done in interrupt
context.  However, we weren't able to get this to work, due to
multiple such UNIT ATTENTION conditions arriving during the rescan,
during updating of the SCSI mid layer, etc.  There's no way to tell
the devices, "stand still while I scan you!"  Since it doesn't work,
there's no point in having the thread, as the rescan triggered via
ioctl or sysfs can be done without such a thread.

Signed-off-by: Mike Miller <mikem@beardog.cce.hp.com>
Signed-off-by: Stephen M. Cameron <scameron@beardog.cce.hp.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>