gpio-mockup-chardev helper has been obsoleted and removed, so also remove
the tools/gpio code that it, and nothing else, was using.
Signed-off-by: Kent Gibson <warthog618@gmail.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>