carl9170: fix bad rssi reading

Fix rssi calculation error which was introduced in otus to ar9170
porting.

Signed-off-by: Hiroaki KAWAI <hiroaki.kawai@gmail.com>
Acked-by: Christian Lamparter <chunkeey@googlemail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
diff --git a/drivers/net/wireless/ath/carl9170/rx.c b/drivers/net/wireless/ath/carl9170/rx.c
index 924135b..d66533c 100644
--- a/drivers/net/wireless/ath/carl9170/rx.c
+++ b/drivers/net/wireless/ath/carl9170/rx.c
@@ -453,7 +453,7 @@
 	/* post-process RSSI */
 	for (i = 0; i < 7; i++)
 		if (phy->rssi[i] & 0x80)
-			phy->rssi[i] = ((phy->rssi[i] & 0x7f) + 1) & 0x7f;
+			phy->rssi[i] = ((~phy->rssi[i] & 0x7f) + 1) & 0x7f;
 
 	/* TODO: we could do something with phy_errors */
 	status->signal = ar->noise[0] + phy->rssi_combined;