ath10k: fix offchan reliability

New firmware revisions don't need peer creation
when doing offchannel tx. Earlier revisions would
queue and never release frames without a peer.

This prevent new firmware revisions from stopping
replenishing wmi-htc tx credits and improves
reliability of offchannel tx which would sometimes
silently fail.

Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>