Add U-Boot replacement loader for the MERCUSYS MR90X. This is required
to increase available flash space in OpenWrt.
Signed-off-by: Mikhail Zhilkin <csharper2005@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/16744
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>