ath9k_hw: clean up hardware revision checks

- AR_SREV_5416_20_OR_LATER is always true, remove it
- AR_SREV_9280_20_OR_LATER is always true within eeprom_4k.c and eeprom_9287.c
- (AR_SREV_9271 || AR_SREV_9285) is always true in eeprom_4k.c

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/eeprom.c b/drivers/net/wireless/ath/ath9k/eeprom.c
index e61404d..e46f751 100644
--- a/drivers/net/wireless/ath/ath9k/eeprom.c
+++ b/drivers/net/wireless/ath/ath9k/eeprom.c
@@ -456,12 +456,7 @@
 		pPdGainBoundaries[i] =
 			min((u16)MAX_RATE_POWER, pPdGainBoundaries[i]);
 
-		if ((i == 0) && !AR_SREV_5416_20_OR_LATER(ah)) {
-			minDelta = pPdGainBoundaries[0] - 23;
-			pPdGainBoundaries[0] = 23;
-		} else {
-			minDelta = 0;
-		}
+		minDelta = 0;
 
 		if (i == 0) {
 			if (AR_SREV_9280_20_OR_LATER(ah))