wl18xx: remove duplicated include from main.c

From: Wei Yongjun <yongjun_wei@trendmicro.com.cn>

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

drivers/net/wireless/ti/wl18xx/main.c

@@ -30,7 +30,6 @@
 #include "../wlcore/acx.h"
 #include "../wlcore/tx.h"
 #include "../wlcore/rx.h"
-#include "../wlcore/io.h"
 #include "../wlcore/boot.h"
 
 #include "reg.h"