ath9k: add debugfs files for reading/writing registers

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath/ath9k/debug.h b/drivers/net/wireless/ath/ath9k/debug.h
index 7314360..5147b87 100644
--- a/drivers/net/wireless/ath/ath9k/debug.h
+++ b/drivers/net/wireless/ath/ath9k/debug.h
@@ -153,6 +153,7 @@
 
 struct ath9k_debug {
 	struct dentry *debugfs_phy;
+	u32 regidx;
 	struct ath_stats stats;
 };