ath5k: correct ath5k signal quality

This adjusts ath5k's signal quality reporting taking into
consideration received beacons at an RSSI of 35 should indicate
you can use of 54 Mbps on a single stream card (all ath5k cards)
reliably.
Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Acked-by: Nick Kossifidis <mickflemm@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath5k/base.c

@@ -1778,7 +1778,17 @@ ath5k_tasklet_rx(unsigned long data)
 
 		rxs.noise = sc->ah->ah_noise_floor;
 		rxs.signal = rxs.noise + rs.rs_rssi;
-		rxs.qual = rs.rs_rssi * 100 / 64;
+
+		/* An rssi of 35 indicates you should be able use
+		 * 54 Mbps reliably. A more elaborate scheme can be used
+		 * here but it requires a map of SNR/throughput for each
+		 * possible mode used */
+		rxs.qual = rs.rs_rssi * 100 / 35;
+
+		/* rssi can be more than 35 though, anything above that
+		 * should be considered at 100% */
+		if (rxs.qual > 100)
+			rxs.qual = 100;
 
 		rxs.antenna = rs.rs_antenna;
 		rxs.rate_idx = ath5k_hw_to_driver_rix(sc, rs.rs_rate);