This commit reconfigures the ap3825i2 in preparation for having it
replace mr16_3. We set up STP, prep some mesh VIFs and match it to the
mr16_3's channels.
Replacing the mr16_3 will fix Matt Woodbury's issues.
I neglected to do this before.
Also, since these conf values now apply everywhere, shift the default
settings for these confs to just vgolan, where they are known-working.
As per openwrt.org[1], the `band` configurable was introduced in
OpenWrt 21.02.2, replacing `hwmode`.
To handle the pre-21.02.2 nodes to which we're deploying, allow us to
configure either of the two (but defaulting hwmode to null).
[1]: https://openwrt.org/docs/guide-user/network/wifi/basic
- Use empty 'ssid:' in your template when you want it to be removed but
the mesh_id added
- Add an stp network.device option so mesh loops don't break things
