brcmsmac: remove duplicated include from debug.c

Remove duplicated include.
Signed-off-by: NWei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

drivers/net/wireless/brcm80211/brcmsmac/debug.c

@@ -21,7 +21,6 @@
 #include <linux/netdevice.h>
 #include <linux/ieee80211.h>
 #include <linux/module.h>
-#include <linux/netdevice.h>
 #include <net/mac80211.h>
 
 #include <defs.h>