ARM: sunxi: dt: Add device tree for Mele A1000

This adds a device tree usable on Mele A1000 (and A2000, as it
apparently is the same device except for the case). This device features
one UART port, Ethernet, an AXP209 PMU on i2c0 and two user configurable
LEDs.

Signed-off-by: Emilio López <emilio@elopez.com.ar>
[maxime: fixed the soc node address]
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>