Back to back fi_write bandwidth testing utility.

Based on simple/pingpong but runs back to back FI-write that focuses on bandwidth test. (comparable to ib_write_bw).
> Should we change all files in the package with dual BSD / GPL-2 license?

Yes - and I just made a note about 30 seconds ago to verify that this is the case.  Anything that is really BSD only needs to be removed, but I'm guessing those are copy-paste header errors.