GPIO selftests have changed to new gpio-mockup-cdev helper, so remove old gpio-mockup-chardev helper. Signed-off-by: Kent Gibson <warthog618@gmail.com> Acked-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>