arm64: allwinner: a64: add device tree for SoPine with baseboard

Pine64 have made an official baseboard when SoPine SoM is out.

The official baseboard is like the original Pine64 -- but with SD card
slot replaced with Pine64's eMMC module slot.

Add a device tree for SoPine with the baseboard.

Signed-off-by: Icenowy Zheng <icenowy@aosc.xyz>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>