ntb_hw_amd: Add memory window support for new AMD hardware

The AMD new hardware uses BAR23 and BAR45 as memory windows
as compared to previos where BAR1, BAR23 and BAR45 is used
for memory windows.

This patch add support for both AMD hardwares.

Signed-off-by: Sanjay R Mehta <sanju.mehta@amd.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>