Comment # 7 on bug 1178274 from Takashi Iwai

Indeed the repo seems to have multiple *.bin files for different versions, and
one must copy it somehow to the right place.

In your case, try to find '*.bin' file under
/lib/firmware/ath11k/QCA6390/hw2.0, and copy or symlink to
/lib/firmware/ath11k/QCA6390/hw2.0 directory.
As far as I see, multiple amss.bin and m3.bin are found:
 
QCA6390/hw2.0/msm/1.0.1.c1.2/WLAN.HST.1.0.1.c1.2-00014-QCAHSTSWPL_SILICONZ-1/amss.bin
 
QCA6390/hw2.0/msm/1.0.1.c1.2/WLAN.HST.1.0.1.c1.2-00014-QCAHSTSWPL_SILICONZ-1/m3.bin
  QCA6390/hw2.0/1.0.1/WLAN.HST.1.0.1-01740-QCAHSTSWPLZ_V2_TO_X86-1/amss.bin
  QCA6390/hw2.0/1.0.1/WLAN.HST.1.0.1-01740-QCAHSTSWPLZ_V2_TO_X86-1/m3.bin
  QCA6390/hw2.0/1.0.1/WLAN.HST.1.0.1-01230-QCAHSTSWPLZ_V2_TO_X86-1/m3.bin
and you'll need to choose one of them.

I have no idea what each subidrectory indicates exactly, so it'll be just a
guess work.