Adding support for VRX518 (and maybe VRX320)

my build
here: openwrt-ipq40xx-generic-avm_fritzbox-7530-squashfs-sysupgrade.bin

whole bin/ folder for what it's worth
fritz7530

I wasn't sure but I made a few changes as well as updating this time, I switched the crc32 algo to 4 bytes as it seems to be a bit faster in the little benchmark at the start

I'm also not quite sure about which wireless driver to use, this one is using the ath10k-ct driver with ct firmware, you lose mesh support (which is an easy way to bridge networks wirelessly) but I personally experienced some kind of regression in speed using the normal driver and firmware, not confirmed on this device though, but on an ipq806x/qca99x0, so i'm not sure, I know the 4019 is different than other chipsets and it has proper reported tx speeds even if you use the default driver and firmware unlike the ipq806x/qca99x0

If you are wondering why DSL doesn't work straight away with this build see here you can also use other blobs if you want checkout the vrx500 section from here

One other thing, you're probably going to want to delete the default watchcat entry in the web interface so it doesnt send pings out, I should probably just remove watchcat altogether since I never get around to doing anything with it anyway