arm64: dts: allwinner: pinephone: Add WiFi support

The PinePhone has a Realtek rtl8723cs WiFi module.

On mainboard revisions 1.0 and 1.1, the reset input is always pulled
high, so no power sequence is needed. On mainboard revision 1.2, the
reset input is connected to PL2.

Signed-off-by: Ondrej Jirman <megous@megous.com>
Signed-off-by: Samuel Holland <samuel@sholland.org>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20201105054135.24860-6-samuel@sholland.org