nds32: Remove duplicated include from pm.c

Remove duplicated include.
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Acked-by: Greentime Hu <greentime@andestech.com>
Signed-off-by: Greentime Hu <greentime@andestech.com>

arch/nds32/kernel/pm.c

@@ -5,7 +5,6 @@
 #include <linux/suspend.h>
 #include <linux/device.h>
 #include <linux/printk.h>
-#include <linux/suspend.h>
 #include <asm/suspend.h>
 #include <nds32_intrinsic.h>