ramips: Add Xiaomi Mi Router 4A 100M International

ramips: Add Xiaomi Mi Router 4A 100M International

The international version of Mi Router 4A 100M is physically
identical to the non-international one, but appears to be
using a different partitioning scheme with the "overlay"
partition being 2MiB in size instead of 1MiB. This means
the following "firmware" partition starts at a different
address and the DTS needs to be adjusted for the firmware
to work.

Signed-off-by: Nita Vesa <werecatf@outlook.com>
(cherry picked from commit 1a8c74da709190e5157af9f5c2502b600f6273bb)
Signed-off-by: Tom Herbers <freifunk@tomherbers.de>