pinctrl: provide new GPIO-to-pinctrl glue helpers

Currently the pinctrl GPIO helpers all take a number from the global
GPIO numberspace - of which we're trying to get rid of as argument.

These helpers are almost universally called from GPIOLIB driver
callbacks which take a pointer to the backing gpio_chip and the
controller-relative offset as arguments.

Let's provide improved variants of these functions that match the
GPIOLIB signatures as the first step in removing the older flavor.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>