We are seeing system hangs during WoWLAN suspend, and get below
two stacks:

Stack1:
[ffffb02cc1557b20] __schedule at ffffffff8bb10860
[ffffb02cc1557ba8] schedule at ffffffff8bb10f24
[ffffb02cc1557bb8] schedule_timeout at ffffffff8bb16d88
[ffffb02cc1557c30] wait_for_completion at ffffffff8bb11778
[ffffb02cc1557c78] __flush_work at ffffffff8b0b30cd
[ffffb02cc1557cf0] __cancel_work_timer at ffffffff8b0b33ad
[ffffb02cc1557d60] ath11k_mac_drain_tx at ffffffffc0c1f0ca [ath11k]
[ffffb02cc1557d70] ath11k_wow_op_suspend at ffffffffc0c5201e [ath11k]
[ffffb02cc1557da8] __ieee80211_suspend at ffffffffc11e2bd3 [mac80211]
[ffffb02cc1557dd8] wiphy_suspend at ffffffffc0f901ac [cfg80211]
[ffffb02cc1557e08] dpm_run_callback at ffffffff8b75118a
[ffffb02cc1557e38] __device_suspend at ffffffff8b751630
[ffffb02cc1557e70] async_suspend at ffffffff8b7519ea
[ffffb02cc1557e88] async_run_entry_fn at ffffffff8b0bf4ce
[ffffb02cc1557ea8] process_one_work at ffffffff8b0b1a24
[ffffb02cc1557ee0] worker_thread at ffffffff8b0b1c4a
[ffffb02cc1557f18] kthread at ffffffff8b0b9cb8
[ffffb02cc1557f50] ret_from_fork at ffffffff8b001d32

Stack2:
[ffffb02cc00b7d18] __schedule at ffffffff8bb10860
[ffffb02cc00b7da0] schedule at ffffffff8bb10f24
[ffffb02cc00b7db0] schedule_preempt_disabled at ffffffff8bb112b4
[ffffb02cc00b7db8] __mutex_lock at ffffffff8bb127ea
[ffffb02cc00b7e38] ath11k_mgmt_over_wmi_tx_work at ffffffffc0c1aa44 [ath11k]
[ffffb02cc00b7ea8] process_one_work at ffffffff8b0b1a24
[ffffb02cc00b7ee0] worker_thread at ffffffff8b0b1c4a
[ffffb02cc00b7f18] kthread at ffffffff8b0b9cb8
[ffffb02cc00b7f50] ret_from_fork at ffffffff8b001d32

From the first stack, ath11k_mac_drain_tx calls
cancel_work_sync(&ar->wmi_mgmt_tx_work) and waits all packets to be sent
out or dropped. However, we find from Stack2 that this work item is blocked
because ar->conf_mutex is already held by ath11k_wow_op_suspend.

Fix this issue by moving ath11k_mac_wait_tx_complete to the start of
ath11k_wow_op_suspend where ar->conf_mutex has not been acquired. And
this change also makes the logic in ath11k_wow_op_suspend match the
logic in ath11k_mac_op_start and ath11k_mac_op_stop.

Tested-on: WCN6855 hw2.0 PCI WLAN.HSP.1.1-03125-QCAHSPSWPL_V1_V2_SILICONZ_LITE-3
Signed-off-by: Baochen Qiang <quic_bqiang@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20220919021435.2459-1-quic_bqiang@quicinc.com