[SCSI] scsi_scan.c: Release mutex in error handling code

The mutex is released on a successful return, so it would seem that it
should be released on an error return as well.

The semantic patch that makes this change is as follows:
(http://www.emn.fr/x-info/coccinelle/)

// <smpl>
@@
expression l;
@@

mutex_lock(l);
... when != mutex_unlock(l)
when any
when strict
(
if (...) { ... when != mutex_unlock(l)
+ mutex_unlock(l);
return ...;
}
|
mutex_unlock(l);
)
// </smpl>

Signed-off-by: Julia Lawall <[e-mail]>
Signed-off-by: James Bottomley <[e-mail]>

drivers/scsi/scsi_scan.c

···
 		printk("%s called twice for host %d", __FUNCTION__,
 				shost->host_no);
 		dump_stack();
+		mutex_unlock(&shost->scan_mutex);
 		return;
 	}