NTB: ntb_test: Update ntb_tool Scratchpad tests

Scratchpad NTB API has changed so has the ntb_tool driver. Outbound
Scratchpad DebugFS files have been moved to peer specific directories.
Each scratchpad is now available via separate file. The test code
has been accordingly altered.

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