scsi: fcoe: convert to use BUS_ATTR_WO

We are trying to get rid of BUS_ATTR() and the usage of that in the fcoe
driver can be trivially converted to use BUS_ATTR_WO(), so use that
instead.

Cc: Johannes Thumshirn <jth@kernel.org>
Cc: "James E.J. Bottomley" <jejb@linux.vnet.ibm.com>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>