sun7i: a20: Add Bananapi M1 Plus support

Banana Pi M1 Plus is an open-source single-board computer
that adds more connectivity to the classic board using
Allwinner A20 SOC.

Bananapi M1-Plus features:
- A20 Dual-core 1.0GHz
- 1 GB DDR3 SDRAM
- MicroSD
- 10/100/1000 Ethernet RJ45
- WiFi b/g/n
- 5V DC Micro USB power-supply

For dts file,
Sync with Linux commit f92ca09("Merge branch 'akpm/master'").

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>