mpt3sas: Move Gen3 HBA's device registration to a separate file

Created a mpt3sas_module.c file for mpt3sas driver where it can register
SAS3 HBA devices with PCI, SML, IOCTL subsystems. Also removed the
corresponding interfaces from mpt3sas_scsih.c file.

Signed-off-by: Sreekanth Reddy <Sreekanth.Reddy@avagotech.com>
Acked-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>