ath11k: remove unneeded flush_workqueue

All work currently pending will be done first by calling destroy_workqueue,
so there is no need to flush it explicitly.
Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: Lv Ruyi (CGEL ZTE) <lv.ruyi@zte.com.cn>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20220301013246.2052570-1-lv.ruyi@zte.com.cn

drivers/net/wireless/ath/ath11k/core.c

@@ -1417,7 +1417,6 @@ EXPORT_SYMBOL(ath11k_core_deinit);
 
 void ath11k_core_free(struct ath11k_base *ab)
 {
-	flush_workqueue(ab->workqueue);
 	destroy_workqueue(ab->workqueue);
 
 	kfree(ab);