arm64: dts: meson-sm1-odroid: set tf_io regulator gpio as open source

According to Odroid-C4 & HC4 Schematics, the TF_3V3N_1V8_EN can be in Hi-Z for 3v3,
and since it's the default GPIOAO_6 mode at reset, let switch this GPIO as Open-Source
to drive for 1, and input for 0.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Acked-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Link: https://lore.kernel.org/r/20210607065435.577334-3-narmstrong@baylibre.com