riscv: nx25: lib: Add relative lib funcs to support RISC-V

Add makefile, interrupts.c and boot.c,... functions
to support RISC-V arch.

Signed-off-by: Rick Chen <rick@andestech.com>
Signed-off-by: Rick Chen <rickchen36@gmail.com>
Signed-off-by: Greentime Hu <green.hu@gmail.com>
Cc: Padmarao Begari <Padmarao.Begari@microsemi.com>
diff --git a/arch/riscv/lib/Makefile b/arch/riscv/lib/Makefile
new file mode 100644
index 0000000..323cf3e
--- /dev/null
+++ b/arch/riscv/lib/Makefile
@@ -0,0 +1,14 @@
+#
+# (C) Copyright 2000-2006
+# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
+#
+# Copyright (C) 2017 Andes Technology Corporation
+# Rick Chen, Andes Technology Corporation <rick@andestech.com>
+#
+# SPDX-License-Identifier:	GPL-2.0+
+#
+
+obj-$(CONFIG_CMD_BOOTM) += bootm.o
+obj-$(CONFIG_CMD_GO) += boot.o
+obj-y	+= cache.o
+obj-y	+= interrupts.o