ARM: dts: sun8i: Add board dts file for Banana Pi M2 Ultra

The Banana Pi M2 Ultra is an SBC based on the Allwinner R40 SoC. The
form factor and position of various connectors, leds and buttons is
similar to the Banana Pi M1+, Banana Pi M3, and is exactly the same
as the latest Banana Pi M64.

It features:

  - X-Powers AXP221s PMIC connected to i2c0
  - 2 GB DDR3 DRAM
  - 8 GB eMMC
  - micro SD card slot
  - DC power jack
  - HDMI output
  - MIPI DSI connector
  - 2x USB 2.0 hosts
  - 1x USB 2.0 OTG
  - gigabit ethernet with Realtek RTL8211E transceiver
  - WiFi/Bluetooth with AP6212 chip, with external antenna connector
  - SATA and power connectors for native SATA support
  - camera sensor connector
  - consumer IR receiver
  - audio out headphone jack
  - onboard microphone
  - red, green, and blue LEDs
  - debug UART pins
  - Li-Po battery connector
  - Raspberry Pi B+ compatible GPIO header
  - power, reset, and boot control buttons

This patch adds a dts file that enables UART, MMC and PMIC support.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>