riscv: nx25: include: Add header files to support RISC-V

Add header files for RISC-V.
Cache, ptregs, data type and other definitions are included.

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>
diff --git a/arch/riscv/include/asm/cache.h b/arch/riscv/include/asm/cache.h
new file mode 100644
index 0000000..facf072
--- /dev/null
+++ b/arch/riscv/include/asm/cache.h
@@ -0,0 +1,22 @@
+/*
+ * Copyright (C) 2017 Andes Technology Corporation
+ * Rick Chen, Andes Technology Corporation <rick@andestech.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0+
+ */
+
+#ifndef _ASM_RISCV_CACHE_H
+#define _ASM_RISCV_CACHE_H
+
+/*
+ * The current upper bound for RISCV L1 data cache line sizes is 32 bytes.
+ * We use that value for aligning DMA buffers unless the board config has
+ * specified an alternate cache line size.
+ */
+#ifdef CONFIG_SYS_CACHELINE_SIZE
+#define ARCH_DMA_MINALIGN	CONFIG_SYS_CACHELINE_SIZE
+#else
+#define ARCH_DMA_MINALIGN	32
+#endif
+
+#endif /* _ASM_RISCV_CACHE_H */