ath9k: add external_reset callback to ath9k_platfom_data for AR9330

The patch adds a callback to ath9k_platform_data. If the
callback is provided by the platform code, then it can be
used to hard reset the WMAC device.

The callback is required for doing a hard reset of the AR9330
chips to get them working again after a hang.

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath/ath9k/hw.h b/drivers/net/wireless/ath/ath9k/hw.h
index 0749fa8..818acdd 100644
--- a/drivers/net/wireless/ath/ath9k/hw.h
+++ b/drivers/net/wireless/ath/ath9k/hw.h
@@ -863,6 +863,7 @@
 
 	bool is_clk_25mhz;
 	int (*get_mac_revision)(void);
+	int (*external_reset)(void);
 };
 
 struct ath_bus_ops {