nds32: Support AG101P serial DM.

Support AG101P serial device tree flow.

Signed-off-by: rick <rick@andestech.com>
diff --git a/arch/nds32/include/asm/config.h b/arch/nds32/include/asm/config.h
index 054cc48..7289217 100644
--- a/arch/nds32/include/asm/config.h
+++ b/arch/nds32/include/asm/config.h
@@ -8,5 +8,6 @@
 
 #ifndef _ASM_CONFIG_H_
 #define _ASM_CONFIG_H_
+#define CONFIG_LMB
 
 #endif