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/cache.c b/arch/riscv/lib/cache.c
new file mode 100644
index 0000000..948656f
--- /dev/null
+++ b/arch/riscv/lib/cache.c
@@ -0,0 +1,50 @@
+/*
+ * Copyright (C) 2017 Andes Technology Corporation
+ * Rick Chen, Andes Technology Corporation <rick@andestech.com>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+
+void flush_dcache_range(unsigned long start, unsigned long end)
+{
+}
+
+void invalidate_icache_range(unsigned long start, unsigned long end)
+{
+}
+
+void invalidate_dcache_range(unsigned long start, unsigned long end)
+{
+}
+
+void flush_cache(unsigned long addr, unsigned long size)
+{
+}
+
+void icache_enable(void)
+{
+}
+
+void icache_disable(void)
+{
+}
+
+int icache_status(void)
+{
+	return 0;
+}
+
+void dcache_enable(void)
+{
+}
+
+void dcache_disable(void)
+{
+}
+
+int dcache_status(void)
+{
+	return 0;
+}