pinctrl: meson: wire up the gpio_chip's set_config callback

pinctrl: meson: wire up the gpio_chip's set_config callback

Use gpiochip_generic_config for the gpio_chip's set_config callback so
GPIO flags like GPIO_PULL_UP or GPIO_PULL_DOWN can be used in the board
.dts descriptions.
This is required for some Meson8m2 boards where GPIO_BSD_EN provides the
"MUTE" signal and requires enabling the internal pull-up resistor.

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Link: https://lore.kernel.org/r/20200417183349.1283092-3-martin.blumenstingl@googlemail.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>