rapidio/tsi721: add DMA engine support

Adds support for DMA Engine API into Tsi721 mport driver.

Includes following changes for Tsi721 driver:
- Modifies BDMA register offset definitions to support per-channel handling
- Separates BDMA channel reserved for RIO Maintenance requests
- Adds DMA Engine callback routines

Signed-off-by: Alexandre Bounine <alexandre.bounine@idt.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Li Yang <leoli@freescale.com>
Cc: Matt Porter <mporter@kernel.crashing.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>