ath9k_hw: reduce ANI firstep range for older chips

Use 0-8 instead of 0-16, which is closer to the old implementation.
Also drop the overwrite of the firstep_low parameter to improve
stability.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath9k/ar5008_phy.c

@@ -1004,11 +1004,9 @@ static bool ar5008_hw_ani_control_new(struct ath_hw *ah,
 	case ATH9K_ANI_FIRSTEP_LEVEL:{
 		u32 level = param;
 
-		value = level * 2;
+		value = level;
 		REG_RMW_FIELD(ah, AR_PHY_FIND_SIG,
 			      AR_PHY_FIND_SIG_FIRSTEP, value);
-		REG_RMW_FIELD(ah, AR_PHY_FIND_SIG_LOW,
-			      AR_PHY_FIND_SIG_FIRSTEP_LOW, value);
 
 		if (level != aniState->firstepLevel) {
 			ath_dbg(common, ANI,