Adding OpenWrt support for OmniTIK 5 PoE ac

This device is very similar to the hap ac, which was supported by ar71xx
Some time ago I built a quick test ath79 qca8k based image for both of these devices. You should be able to get some hints from it at least: omni ac
It worked for me at the time, and given my device is now functioning, and out-of-reach, I have been reluctant to change it.

Not submitted to Openwrt:

  • master ath79/mikrotik does not use qca8k
  • kernel 5.4 qca8k does not support switch vlan offloading, and the backport is not straightforwards
  • on the hap ac I could not get the SFP port functioning correctly (needed fixed-link, and link reset).
  • voltage / temp sensor support not included (kernel driver works, but needs hacky DTS)
  • PoE control not supported (no kernel driver, but may be third party: see mtpoe_ctrl rb750r2 rb960pgs)