sunxi: a64: Add a defconfig for the PinePhone

sunxi: a64: Add a defconfig for the PinePhone

The PinePhone is a smartphone produced by Pine64, with an A64 SoC,
2 or 3 GiB LPDDR3 RAM, 16 or 32 GiB eMMC, 720x1440 MIPI-DSI panel,
and Quectel EG25-G modem.

There are two main board revisions: 1.1 for early adopters, and 1.2
for mass production. Since there is code to detect the board revision
at boot, one config/image can support both boards.

Acked-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Samuel Holland <samuel@sholland.org>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Andre Przywara <andre.przywara@arm.com>