scsi: mpt3sas: Introduce function to clone mpi request.

1) Added function _base_clone_mpi_to_sys_mem to clone
MPI request into system BAR0 mapped region.

2) Separate out MPI Endpoint IO submissions to function
_base_put_smid_mpi_ep_scsi_io.

3) MPI EP requests are submitted in two 32 bit MMIO writes.
from _base_mpi_ep_writeq.

 For 32 bit Arch,_base_writeq function is identical
to _base_mpi_ep_writeq, Removed duplicate code as suggested.

Signed-off-by: Suganath Prabu S <suganath-prabu.subramani@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>