riscv: Correct a comment in io.h

Replace NDS32 with RISC-V in the comments.

Signed-off-by: Bin Meng <bmeng@tinylab.org>
Reviewed-by: Rick Chen <rick@andestech.com>
diff --git a/arch/riscv/include/asm/io.h b/arch/riscv/include/asm/io.h
index 220266e..b16e6df 100644
--- a/arch/riscv/include/asm/io.h
+++ b/arch/riscv/include/asm/io.h
@@ -180,7 +180,7 @@
  *  IO port access primitives
  *  -------------------------
  *
- * The NDS32 doesn't have special IO access instructions just like ARM;
+ * The RISC-V doesn't have special IO access instructions just like ARM;
  * all IO is memory mapped.
  * Note that these are defined to perform little endian accesses
  * only.  Their primary purpose is to access PCI and ISA peripherals.