board: Add Bananapi M1 support

Add initial support for bananapi M1 board with below features:
- U-Boot 2017.09
- Linux 4.13.7
- Default packages from buildroot

Cc: Jason <manager@sinovoip.com.cn>
Cc: hailymei@banana-pi.com <hailymei@banana-pi.com>
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>