wifi: rtw89: refine packet offload delete flow of 6 GHz probe

There are two places where offload packets of 6 GHz probe would be deleted
from FW, i.e. calling rtw89_fw_h2c_del_pkt_offload().
* rtw89_core_cancel_6ghz_probe_tx()
* rtw89_release_pkt_list()
It is possible that we try to delete the same one from FW twice. Although
it might not be a big problem for now, it will depend on the runtime chip
firmware. So, we add a check to avoid it. In case things becomes complex
due to racing problem, we don't choose to do list_del(info->list) and
kfree(info) in both sides.

Besides, rtw89_fw_h2c_del_pkt_offload() will needs to wait for completion
after the follow-up commit. However, rtw89_core_cancel_6ghz_probe_tx()
was called in interrupt context. So, we move the stuffs of calling
rtw89_fw_h2c_del_pkt_offload() from rtw89_core_cancel_6ghz_probe_tx()
into a work. Then, we also need a check there before we call it.

Signed-off-by: Zong-Zhe Yang <kevin_yang@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/091966e5709cd7caecf9b81f7fd6388ae2b70a7e.camel@realtek.com