gpio: Remove obsolete comment about gpiochip_free_hogs() usage

gpiochip_free_hogs() was always called from gpiochip_remove(), not
of_gpiochip_remove().  It is now also called from the failure patch in
gpiochip_add_data_with_key().

Fixes: f625d460 ("gpio: add GPIO hogging mechanism")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>