configs/bananapi_m2_zero: new defconfig

The Banana Pi M2 Zero [1] is a board from Sinovoip, based on the
Allwinner H2+ SoC.

It is similar to the other Banana Pi M2* boards, from which this
configuration is inspired.

[1]: http://www.banana-pi.org/m2z.html



Signed-off-by: Vincent Stehlé <vincent.stehle@laposte.net>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>