libertas: firmware.c: remove duplicated include

Signed-off-by: Duan Jiong <djduanjiong@gmail.com>

drivers/net/wireless/libertas/firmware.c

@@ -4,9 +4,7 @@
 
 #include <linux/sched.h>
 #include <linux/firmware.h>
-#include <linux/firmware.h>
 #include <linux/module.h>
-#include <linux/sched.h>
 
 #include "dev.h"
 #include "decl.h"