tftp: implement support for LED activity

Implement support for LED activity. If the feature is enabled,
make the defined ACTIVITY LED to signal traffic.

Also turn the ACTIVITY LED OFF if a CTRL-C is detected in the main
net loop function.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
2 files changed