selftests: remove obsolete gpio references from kselftest_deps.sh

GPIO Makefile has been greatly simplified so remove references to lines
which no longer exist.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>