ath9k: make ath9k_common_ops const

As noted by Jiri.

Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath/ath9k/main.c b/drivers/net/wireless/ath/ath9k/main.c
index ab9b7ea..2278dcb 100644
--- a/drivers/net/wireless/ath/ath9k/main.c
+++ b/drivers/net/wireless/ath/ath9k/main.c
@@ -1579,7 +1579,7 @@
 	return val;
 }
 
-static struct ath_ops ath9k_common_ops = {
+static const struct ath_ops ath9k_common_ops = {
 	.read = ath9k_ioread32,
 	.write = ath9k_iowrite32,
 };