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>