ath6kl: create ath6kl_hif_stop()

This is to reset hif layer for powering down hw.

Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>

drivers/net/wireless/ath/ath6kl/hif.h

@@ -246,6 +246,7 @@ struct ath6kl_hif_ops {
 	int (*resume)(struct ath6kl *ar);
 	int (*power_on)(struct ath6kl *ar);
 	int (*power_off)(struct ath6kl *ar);
+	void (*stop)(struct ath6kl *ar);
 };
 
 int ath6kl_hif_setup(struct ath6kl_device *dev);