ath9k: Use helpers

Break down huge functions, use helper functions or
macros instead.
Signed-off-by: Sujith <Sujith.Manoharan@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath9k/rc.h

@@ -27,6 +27,11 @@ struct ath_softc;
 #define RATE_TABLE_SIZE  64
 #define MAX_TX_RATE_PHY  48
 
+/* VALID_ALL - valid for 20/40/Legacy,
+ * VALID - Legacy only,
+ * VALID_20 - HT 20 only,
+ * VALID_40 - HT 40 only */
+
 #define INVALID    0x0
 #define VALID      0x1
 #define VALID_20   0x2