[SCSI] ipr: missing unlock before a return

We recently changed the locking in this function, but this return was
missed.  It needs an unlock and the IRQs need to be restored.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>