scsi: mpt3sas: Introduce API to get BAR0 mapped buffer address

For MPI Endpoint/Mcpu, driver should double buffer data buffer/SGLs.
This is normally copied from host to internal memory of IOC by DMA
engine of PCI device. Since the interface to DMA from host to mCPU is
not present for Mcpu/MPI Endpoint device, driver does double copy of
those buffers directly to the mCPU memory region via BAR0 region.

Introduced API to calculate and return BAR0 mapped host buffer's
physical and virtual address for the provided smid.

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