this adds support for devices with cellular modems, like the GL-inet
XE300

Some devices (e.g. TP-Link RE450) only have 6 MB available space. That's
not enough to hold all the stuff e.g. ca-certs. So only build
ca-certificates, airtime stats etc. when we have enough flash.

For now, leave gitlab.freifunk-stuttgart.de in place

We were expecting a checked out branch which obviously isn't always the
case. Instread try and find a tag.

Add support for Watchguard Firewall X750e

See merge request !8

when running opkg update, this currently results in errors like this:

Downloading https://downloads.openwrt.org/releases/22.03-SNAPSHOT/packages/arm_cortex-a7_neon-vfpv4/base/Packages.gz
wget: SSL support not available, please install one of the libustream-.*[ssl|tls] packages as well as the ca-bundle and ca-certificates packages.
*** Failed to download the package list from https://downloads.openwrt.org/releases/22.03-SNAPSHOT/packages/arm_cortex-a7_neon-vfpv4/base/Packages.gz

since we already have wolfssl for hostapd stuff, just install
libustream-wolfssl and ca-certificates.