wl1251: remove depcreated qual usage

Fixes warnings:

drivers/net/wireless/wl12xx/wl1251_rx.c: In function 'wl1251_rx_status':
drivers/net/wireless/wl12xx/wl1251_rx.c:75:
  warning: 'qual' is deprecated (declared at include/net/mac80211.h:555)
drivers/net/wireless/wl12xx/wl1251_rx.c:77:
  warning: 'qual' is deprecated (declared at include/net/mac80211.h:555)
drivers/net/wireless/wl12xx/wl1251_rx.c:77:
  warning: 'qual' is deprecated (declared at include/net/mac80211.h:555)
drivers/net/wireless/wl12xx/wl1251_rx.c:77:
  warning: 'qual' is deprecated (declared at include/net/mac80211.h:555)
drivers/net/wireless/wl12xx/wl1251_rx.c:78:
  warning: 'qual' is deprecated (declared at include/net/mac80211.h:555)
drivers/net/wireless/wl12xx/wl1251_rx.c:78:
  warning: 'qual' is deprecated (declared at include/net/mac80211.h:555)
drivers/net/wireless/wl12xx/wl1251_rx.c:78:
  warning: 'qual' is deprecated (declared at include/net/mac80211.h:555)

Signed-off-by: Kalle Valo <kalle.valo@nokia.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>