Offchannel management frames were failing:

[18099.253732] ath10k_pci 0000:01:00.0: timed out waiting for offchannel skb cf0e3780
[18102.293686] ath10k_pci 0000:01:00.0: timed out waiting for offchannel skb cf0e3780
[18105.333653] ath10k_pci 0000:01:00.0: timed out waiting for offchannel skb cf0e3780
[18108.373712] ath10k_pci 0000:01:00.0: timed out waiting for offchannel skb cf0e3780
[18111.413687] ath10k_pci 0000:01:00.0: timed out waiting for offchannel skb cf0e36c0
[18114.453726] ath10k_pci 0000:01:00.0: timed out waiting for offchannel skb cf0e3f00
[18117.493773] ath10k_pci 0000:01:00.0: timed out waiting for offchannel skb cf0e36c0
[18120.533631] ath10k_pci 0000:01:00.0: timed out waiting for offchannel skb cf0e3f00

This bug appears to have been added between 4.0 (which works for us),
and 4.4, which does not work.

I think this is because the tx-offchannel logic gets in a loop when
ath10k_mac_tx_frm_has_freq(ar) is false, so pkt is never actually
sent to the firmware for transmit.

This patch fixes the problem on 4.9 for me, and now HS20 clients
can work again with my firmware.

Antonio: tested with 10.4-3.5.3-00057 on QCA4019 and QCA9888
Signed-off-by: Ben Greear <greearb@candelatech.com>
Tested-by: Antonio Quartulli <antonio.quartulli@kaiwoo.ai>
[kvalo@codeaurora.org: improve commit log, remove unneeded parenthesis]
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>