scsi: drop bus reset for wd33c93-compatible boards

The bus reset function is just a wrapper calling host reset under the
host lock. So move taking of the host lock into the host reset function
and drop bus reset.

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>