scsi: mpt3sas: Fix for regression caused by sparse cleanups

Commit cf6bf971

 ("scsi: mpt3sas: Bug fix for big endian systems") was
merged to address sparse warnings. However, the patch introduced a
regression on big endian since the code accidentally mixed I/O memory
accessors, which do endian swaps, and regular CPU loads and stores.

Do a partial revert of the offending commit.

[mkp: replaced commit message]

Signed-off-by: Chaitra P B <chaitra.basappa@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>