gpio: gpio-by-pinctrl: s/used to do/is used to do/

gpio: gpio-by-pinctrl: s/used to do/is used to do/

Add missing "is" to the driver's help text ("used to do" has a
completely different meaning).

Fixes: 7671f4949a6c9111 ("gpio: gpio-by-pinctrl: add pinctrl based generic GPIO driver")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Linus Walleij <linusw@kernel.org>
Link: https://patch.msgid.link/b1ecb31a37f8e35447122554a38985cb6240eb11.1775556619.git.geert+renesas@glider.be
[Bartosz: tweak the help text even more]
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>