mvebu: Add basic support for WRT1900AC (v1) and Turris Omnia (pre 2019)
This adds basic support for the WRT1900AC and Turris Omnia. In order
to continue to use these as wifi routers, some or all of the wifi
modules will need to be replaced, preferably with an ath9k based
chipset. Keep in mind that not all ath9k chipsets work well in
AP mode.
WRT1900AC:
* The original issue with this router, in addition to the non-free
wifi, was an init / learning blob needed for the DDR3 memory. This
issue was resolved in 2015, but there were some stability issues.
* The Marvell wifi chipset is not supported and will need to be
removed or replaced.
* RISCi_ATOM was not able to successfully flash upstream u-boot.
It's most likely a configuration or build issue.
* libreCMC can be installed from the stock firmware web-ui using
the *-factory.img.
Turris Omnnia:
* The ath10k wifi chipset will need to be removed.
* Full support is not ready yet; it works with some hacks.
* Upstream u-boot can be built and flashed; the libreCMC
toolchain was used to build it.
Taken from upstrem openwrt-19.07 @
153392e209c5110448db9e1e7ce9a3566f124b37