ath5k: initialize default noise floor

Initialize noise floor variable with a default of -95. This was used
uninitialized in the signal strength (RSSI -> dBm) conversion until the first
noise floor calibration was completed.
Signed-off-by: NBruno Randolf <br1@einfach.org>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath5k/attach.c

@@ -123,6 +123,7 @@ int ath5k_hw_attach(struct ath5k_softc *sc)
 	ah->ah_limit_tx_retries = AR5K_INIT_TX_RETRY;
 	ah->ah_software_retry = false;
 	ah->ah_ant_mode = AR5K_ANTMODE_DEFAULT;
+	ah->ah_noise_floor = -95;	/* until first NF calibration is run */
 
 	/*
 	 * Find the mac version