NTB: ntb_test: Add ntb_tool Message tests

Messages NTB API is now available. ntb_tool driver has been altered
to perform messages send and receive operation. The test of messages
read/write to/from peer device has been added to the script.

Signed-off-by: Serge Semin <fancer.lancer@gmail.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>