nds32: Support AE3XX platform.

Support Andestech AE3xx platform: serial, timer device tree flow.

Signed-off-by: rick <rick@andestech.com>
diff --git a/arch/nds32/cpu/n1213/Makefile b/arch/nds32/cpu/n1213/Makefile
index 7d5ae96..3a9ada1 100644
--- a/arch/nds32/cpu/n1213/Makefile
+++ b/arch/nds32/cpu/n1213/Makefile
@@ -12,3 +12,4 @@
 extra-y	= start.o
 
 obj-$(if $(filter ag101,$(SOC)),y) += ag101/
+obj-$(if $(filter ae3xx,$(SOC)),y) += ae3xx/