pinctrl: meson: Fix GPIO direction registers access

The macros used to set the direction of the GPIO pins are misused,
resulting in a wrong behavior when trying to read the GPIO input level
from U-Boot.

A better macro is also used when setting the output direction.

Signed-off-by: Carlo Caione <ccaione@baylibre.com>
Reviewed-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>