NTB: unify translation addresses

There is no need for the upstream and downstream addresses to be different
for the NTB configs. Go to using a single set of address. It is still
possible to configure them differently using module parameter override
however.

Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Acked and Tested-by: Allen Hubbe <Allen.Hubbe@emc.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>