This creates a DTSI for Xiaomi devices with 128M NAND.
This allows to consolidate the partitions and a few other nodes for
AC2100 family and Mi Router 3G.
Note that the Mi Router 3 Pro has 256M NAND and differently sized
partitions.
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>