nds32: bootm: Fix warning of struct tag_serialnr declared

move #include <asm/setup.h> from bootm.c to bootm.h

Signed-off-by: rick <rick@andestech.com>
diff --git a/arch/nds32/include/asm/bootm.h b/arch/nds32/include/asm/bootm.h
index 6b10c07..2e2fe01 100644
--- a/arch/nds32/include/asm/bootm.h
+++ b/arch/nds32/include/asm/bootm.h
@@ -11,6 +11,8 @@
 #ifndef NDS32_BOOTM_H
 #define NDS32_BOOTM_H
 
+#include <asm/setup.h>
+
 extern void udc_disconnect(void);
 
 #if defined(CONFIG_SETUP_MEMORY_TAGS) || \