rtl8180: Remove usage of deprecated 'qual'

When building rtl8180, the following warning occurs:

  CC [M]  drivers/net/wireless/rtl818x/rtl8180_dev.o
drivers/net/wireless/rtl818x/rtl8180_dev.c: In function ‘rtl8180_handle_rx’:
drivers/net/wireless/rtl818x/rtl8180_dev.c:135: warning: ‘qual’ is deprecated
    (declared at include/net/mac80211.h:562)
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/rtl818x/rtl8180_dev.c

@@ -132,7 +132,6 @@ static void rtl8180_handle_rx(struct ieee80211_hw *dev)
 
 			rx_status.antenna = (flags2 >> 15) & 1;
 			/* TODO: improve signal/rssi reporting */
-			rx_status.qual = flags2 & 0xFF;
 			rx_status.signal = (flags2 >> 8) & 0x7F;
 			/* XXX: is this correct? */
 			rx_status.rate_idx = (flags >> 20) & 0xF;