gpio: emulate open drain & open source in dm_gpio_set_value()

Handle the GPIOD_OPEN_DRAIN & GPIOD_OPEN_SOURCE flags to emulate open drain
and open source by setting the GPIO line as input depending on the
requested value.

The behaviour is taken from the Linux gpiolib.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Simon Glass <sjg@chromium.org>