[SCSI] hpsa: do not sleep in atomic context in rmmod path.

Don't call kthread_stop with a spin lock held and interrupts
disabled because kthread_stop will sleep waiting for the thread
to stop.

Signed-off-by: Stephen M. Cameron <scameron@beardog.cce.hp.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>