ath10k: Fix the race condition in firmware dump work queue

There is a race condition, when the user writes 'hw-restart' and
'hard' in the simulate_fw_crash debugfs file without any delay.
In the above scenario, the firmware dump work queue(scheduled by
'hard') should be handled gracefully, while the target is in the
'hw-restart'.

Tested HW: QCA9984
Tested FW: 10.4-3.9.0.2-00044
Co-developed-by: Govindaraj Saminathan <gsamin@codeaurora.org>
Signed-off-by: Govindaraj Saminathan <gsamin@codeaurora.org>
Signed-off-by: Maharaja Kennadyrajan <mkenna@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/1585213077-28439-1-git-send-email-mkenna@codeaurora.org

drivers/net/wireless/ath/ath10k/pci.c

@@ -2074,6 +2074,7 @@ static void ath10k_pci_hif_stop(struct ath10k *ar)
 	ath10k_pci_irq_sync(ar);
 	napi_synchronize(&ar->napi);
 	napi_disable(&ar->napi);
+	cancel_work_sync(&ar_pci->dump_work);
 
 	/* Most likely the device has HTT Rx ring configured. The only way to
 	 * prevent the device from accessing (and possible corrupting) host