rapidio/tsi721: modify PCIe capability settings

Modify initialization of PCIe capability registers in Tsi721 mport driver:
 - change Completion Timeout value to avoid unexpected data transfer
   aborts during intensive traffic.
 - replace hardcoded offset of PCIe capability block by making it use the
   common function.

This patch is applicable to kernel versions starting from 3.2-rc1.

Signed-off-by: Alexandre Bounine <alexandre.bounine@idt.com>
Cc: Matt Porter <mporter@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>