NTB: ntb_tool: Add full multi-port NTB API support

Former NTB Debugging tool driver supported only the limited
functionality of the recently updated NTB API, which is now available
to work with the truly NTB multi-port devices and devices, which
got NTB Message registers instead of Scratchpads. This patch
fully rewrites the driver so one would fully expose all the new
NTB API interfaces. Particularly it concerns the Message registers,
peer ports API, NTB link settings. Additional cleanups are also added
here.

Signed-off-by: Serge Semin <[email protected]>
Signed-off-by: Jon Mason <[email protected]>