riscv: Avoid the reserved memory fixup if src and dst point to the same place

The copy of reserved memory node from source dtb to destination dtb
can be avoided if they point to the same place. This is useful when
OF_PRIOR_STAGE is used.
Signed-off-by: NBin Meng <bin.meng@windriver.com>
Reviewed-by: NRick Chen <rick@andestech.com>
Reviewed-by: NAtish Patra <atish.patra@wdc.com>

arch/riscv/lib/fdt_fixup.c

@@ -82,10 +82,9 @@ int riscv_fdt_copy_resv_mem_node(const void *src, void *dst)
  * @fdt: Pointer to the device tree in which reserved memory node needs to be
  *	 added.
  *
- * In RISC-V, any board compiled with OF_SEPARATE needs to copy the reserved
- * memory node from the device tree provided by the firmware to the device tree
- * used by U-Boot. This is a common function that individual board fixup
- * functions can invoke.
+ * In RISC-V, any board needs to copy the reserved memory node from the device
+ * tree provided by the firmware to the device tree used by U-Boot. This is a
+ * common function that individual board fixup functions can invoke.
  *
  * Return: 0 on success or error otherwise.
  */
@@ -95,6 +94,11 @@ int riscv_board_reserved_mem_fixup(void *fdt)
 	void *src_fdt_addr;
 
 	src_fdt_addr = map_sysmem(gd->arch.firmware_fdt_addr, 0);
+
+	/* avoid the copy if we are using the same device tree */
+	if (src_fdt_addr == fdt)
+		return 0;
+
 	err = riscv_fdt_copy_resv_mem_node(src_fdt_addr, fdt);
 	if (err < 0)
 		return err;