ntb_test: Add a selftest script for the NTB subsystem

This script automates testing doorbells, scratchpads and memory windows
for an NTB device. It can be run locally, with the NTB looped
back to the same host or use SSH to remotely control the second host.

In the single host case, the script just needs to be passed two
arguments: a PCI ID for each side of the link. In the two host case
the -r option must be used to specify the remote hostname (which must
be SSH accessible and should probably have ssh-keys exchanged).

A sample run looks like this:

$ sudo ./ntb_test.sh 0000:03:00.1 0000:83:00.1 -p 29
Starting ntb_tool tests...
Running link tests on: 0000:03:00.1 / 0000:83:00.1
  Passed
Running link tests on: 0000:83:00.1 / 0000:03:00.1
  Passed
Running db tests on: 0000:03:00.1 / 0000:83:00.1
  Passed
Running db tests on: 0000:83:00.1 / 0000:03:00.1
  Passed
Running spad tests on: 0000:03:00.1 / 0000:83:00.1
  Passed
Running spad tests on: 0000:83:00.1 / 0000:03:00.1
  Passed
Running mw0 tests on: 0000:03:00.1 / 0000:83:00.1
  Passed
Running mw0 tests on: 0000:83:00.1 / 0000:03:00.1
  Passed
Running mw1 tests on: 0000:03:00.1 / 0000:83:00.1
  Passed
Running mw1 tests on: 0000:83:00.1 / 0000:03:00.1
  Passed

Starting ntb_pingpong tests...
Running ping pong tests on: 0000:03:00.1 / 0000:83:00.1
  Passed

Starting ntb_perf tests...
Running local perf test without DMA
  0: copied 536870912 bytes in 164453 usecs, 3264 MBytes/s
  Passed
Running remote perf test without DMA
  0: copied 536870912 bytes in 164453 usecs, 3264 MBytes/s
  Passed

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Acked-by: Shuah Khan <shuahkh@osg.samsung.com>
Acked-by: Allen Hubbe <Allen.Hubbe@emc.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>