gpiolib: of: factor out code overriding gpio line polarity

[ Upstream commit e3186e36 ]

There are several instances where we use a separate property to
override polarity specified in gpio property. Factor it out into
a separate function.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Stable-dep-of: f8d76c2c ("gpiolib: of: add polarity quirk for TSC2005")
Signed-off-by: Sasha Levin <sashal@kernel.org>