ath9k_hw: simplify noisefloor calibration chainmask calculation

The noisefloor array index always corresponds to the rx chain number it
belongs to (with an offset of 3 for the extension chain).

It's much simpler (and actually more correct) to directly use the
chainmask to calculate the bitmask for the noisefloor array, instead of
using these weird chip revision checks and hardcoded mask values.

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/calib.c b/drivers/net/wireless/ath/ath9k/calib.c
index 0737246..139289e 100644
--- a/drivers/net/wireless/ath/ath9k/calib.c
+++ b/drivers/net/wireless/ath/ath9k/calib.c
@@ -172,26 +172,9 @@
 	struct ath9k_nfcal_hist *h;
 	unsigned i, j;
 	int32_t val;
-	u8 chainmask;
+	u8 chainmask = (ah->rxchainmask << 3) | ah->rxchainmask;
 	struct ath_common *common = ath9k_hw_common(ah);
 
-	if (AR_SREV_9300_20_OR_LATER(ah))
-		chainmask = 0x3F;
-	else if (AR_SREV_9285(ah) || AR_SREV_9271(ah))
-		chainmask = 0x9;
-	else if (AR_SREV_9280(ah) || AR_SREV_9287(ah)) {
-		if ((ah->rxchainmask & 0x2) || (ah->rxchainmask & 0x4))
-			chainmask = 0x1B;
-		else
-			chainmask = 0x09;
-	} else {
-		if (ah->rxchainmask & 0x4)
-			chainmask = 0x3F;
-		else if (ah->rxchainmask & 0x2)
-			chainmask = 0x1B;
-		else
-			chainmask = 0x09;
-	}
 	h = ah->nfCalHist;
 
 	for (i = 0; i < NUM_NF_READINGS; i++) {