tools/blobtool: Rearrange string swapping in run_buffer()
tools/blobtool: Rearrange string swapping in run_buffer()

- Simplify run_buffer() by unconditionally swapping input and output
strings after every action, and then swapping one more time at the
end to place the output string in the right place.  This also eliminates
the need for the operations counter and special handling of the no-op
(pass-through) case.

cmusatyalab/openisr,cmusatyalab/openisr,cmusatyalab/openisr,cmusatyalab/openisr,cmusatyalab/openisr