ar71xx: add support for Gainstrong MiniBox V3.2
Adds MiniBox V3.2 ar71xx target (QCA99531 + QCA9887)
Info: http://oolite.cn/minibox-v3-2-qca9531-qca9887-module-pin-specification.html
Reference patch: http://oolite.cn/wp-content/uploads/2017/09/minibox_v3_cc15.05_20160325.patch
Installation: Upload firmware to uboot via HTTP at 192.168.1.1 (press button for 5 seconds)
Signed-off-by: Pau Escrich <p4u@dabax.net>
Signed-off-by: Daniel Golle <daniel@makrotopia.org>
(daniel@makrotopia.org: rebased and fixed conflicts, fixed LED name,
added ath10k eeprom)