scsi: megaraid_mbox: drop duplicate bus reset and device reset function

megaraid_mbox only has one reset function, and that is a host reset.  So
drop the duplicate bus reset and device reset functions.

Signed-off-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>