ath9k_hw: fix fast clock handling for 5GHz channels

Combine multiple checks that were supposed to check for the same
conditions, but didn't. Always enable fast PLL clock on AR9280 2.0

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/ar9002_phy.c b/drivers/net/wireless/ath/ath9k/ar9002_phy.c
index 18cfe1a..ed314e8 100644
--- a/drivers/net/wireless/ath/ath9k/ar9002_phy.c
+++ b/drivers/net/wireless/ath/ath9k/ar9002_phy.c
@@ -455,16 +455,12 @@
 		pll |= SM(0x2, AR_RTC_9160_PLL_CLKSEL);
 
 	if (chan && IS_CHAN_5GHZ(chan)) {
-		pll |= SM(0x28, AR_RTC_9160_PLL_DIV);
-
-
-		if (AR_SREV_9280_20(ah)) {
-			if (((chan->channel % 20) == 0)
-			    || ((chan->channel % 10) == 0))
-				pll = 0x2850;
-			else
-				pll = 0x142c;
-		}
+		if (IS_CHAN_A_FAST_CLOCK(ah, chan))
+			pll = 0x142c;
+		else if (AR_SREV_9280_20(ah))
+			pll = 0x2850;
+		else
+			pll |= SM(0x28, AR_RTC_9160_PLL_DIV);
 	} else {
 		pll |= SM(0x2c, AR_RTC_9160_PLL_DIV);
 	}