[SCSI] mpt3sas: add new driver supporting 12GB SAS

These driver files are initially, substantially similar to mpt2sas but,
because mpt2sas is going into maintenance mode and mp3sas will become heavily
developed, we elected to keep the code bases separate.

Signed-off-by: Sreekanth Reddy <Sreekanth.Reddy@lsi.com>
Reviewed-by: Nagalakshmi Nandigama <Nagalakshmi.Nandigama@lsi.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>