staging: wlan-ng: add missing byte order conversion
Conversion macros le16_to_cpu was removed and that caused new sparse warning
sparse output:
drivers/staging/wlan-ng/p80211netdev.c:241:44: warning: incorrect type in argument 2 (different base types)
drivers/staging/wlan-ng/p80211netdev.c:241:44: expected unsigned short [unsigned] [usertype] fc
drivers/staging/wlan-ng/p80211netdev.c:241:44: got restricted __le16 [usertype] fc