Fix flashing of hex format files
Fix flashing of hex format files

When trying to flash a hex format file we get a TypeError from the lambda
function:

flash_tool.py", line 116, in ranges
    for a, b in itertools.groupby(enumerate(i), lambda x, y: y - x):
TypeError: <lambda>() takes exactly 2 arguments (1 given)

This was introduced when the codebase was updated to support python3.  Make
the lambda function lambda x: x[1] - x[0].

Fixes #378

Signed-off-by: Kumar Gala <a5e5248af4cd4f0ed8c515f61d40a6e2db46a66e@gmail.com>

mesheven/pyOCD,pyocd/pyOCD,mbedmicro/pyOCD,flit/pyOCD,mesheven/pyOCD,pyocd/pyOCD,mbedmicro/pyOCD,flit/pyOCD,mbedmicro/pyOCD,mesheven/pyOCD