R1350 upstream ath10k A/B test image

Purpose: compare severe 5 GHz TX weakness seen with ath10k-ct.
Only wireless driver/firmware changed:
  CT: kmod-ath10k-ct + ath10k-firmware-qca9888-ct
  This image: kmod-ath10k + ath10k-firmware-qca9888
DTS, ART pre-calibration, flash layout and OpenWrt base are unchanged.

Prefer initramfs RAM boot. If sysupgrade is used, have serial/programmer recovery ready.
After boot set 5G channel 149 / VHT80 / CN, connect the same client at the same position,
then record:
  dmesg | grep -i ath10k
  iw dev phy0-ap0 station dump
  iw dev phy0-ap0 info
  WinFi RSSI screenshot
