scsi: megaraid_sas: Create separate functions for allocating and freeing controller...

scsi: megaraid_sas: Create separate functions for allocating and freeing controller DMA buffers

Code refactoring - create separate functions to allocate and free
controller DMA buffers.

Rebased for UEK kernel.

Signed-off-by: Kashyap Desai <kashyap.desai@broadcom.com>
Signed-off-by: Shivasharan S <shivasharan.srikanteshwara@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sumit Saxena <sumit.saxena@broadcom.com>
Orabug: 27625001
Signed-off-by: Jack Vogel <jack.vogel@oracle.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>