scsi: fix comment in scsi_device_set_state()

The function returns '0' if successful; with the original comment
the function doesn't have a way to indicate success ...
Signed-off-by: NHannes Reinecke <hare@suse.de>
Reviewed-by: NBart van Assche <bvanassche@wdc.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NJohannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/scsi_lib.c

@@ -2548,7 +2548,7 @@ EXPORT_SYMBOL(scsi_test_unit_ready);
  *	@sdev:	scsi device to change the state of.
  *	@state:	state to change to.
  *
- *	Returns zero if unsuccessful or an error if the requested 
+ *	Returns zero if successful or an error if the requested
  *	transition is illegal.
  */
 int