ath5k: fix build break from "ath5k: Print out opmode in debugfs"

Also improve ath_opmode_to_string usage by having it return UNKNOWN
rather than NULL in the event of failure to map the opmode value to a
representative string.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath/debug.h b/drivers/net/wireless/ath/debug.h
index a3a5a62..64e4af2 100644
--- a/drivers/net/wireless/ath/debug.h
+++ b/drivers/net/wireless/ath/debug.h
@@ -78,6 +78,13 @@
 #endif /* CONFIG_ATH_DEBUG */
 
 /** Returns string describing opmode, or NULL if unknown mode. */
+#ifdef CONFIG_ATH_DEBUG
 const char *ath_opmode_to_string(enum nl80211_iftype opmode);
+#else
+static inline const char *ath_opmode_to_string(enum nl80211_iftype opmode)
+{
+	return "UNKNOWN";
+}
+#endif
 
 #endif /* ATH_DEBUG_H */