regulator: da9211: Pass descriptors instead of GPIO numbers

This augments the DA9211 regulator driver to fetch its GPIO descriptors
directly from the device tree using the newly exported
devm_get_gpiod_from_child().

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Mark Brown <broonie@kernel.org>