of: Always unflatten in unflatten_and_copy_device_tree()

We want to populate an empty DT whenever CONFIG_OF is enabled so that
overlays can be applied and the DT unit tests can be run. Make
unflatten_and_copy_device_tree() stop printing a warning if the
'initial_boot_params' pointer is NULL. Instead, simply copy the dtb if
there is one and then unflatten it. If there isn't a DT to copy, then
the call to unflatten_device_tree() is largely a no-op, so nothing
really changes here.

Cc: Rob Herring <robh+dt@kernel.org>
Cc: Frank Rowand <frowand.list@gmail.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lore.kernel.org/r/20240217010557.2381548-2-sboyd@kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>

drivers/of/fdt.c

@@ -1318,6 +1318,21 @@ bool __init early_init_dt_scan(void *params)
 	return true;
 }
 
+static void *__init copy_device_tree(void *fdt)
+{
+	int size;
+	void *dt;
+
+	size = fdt_totalsize(fdt);
+	dt = early_init_dt_alloc_memory_arch(size,
+					     roundup_pow_of_two(FDT_V17_SIZE));
+
+	if (dt)
+		memcpy(dt, fdt, size);
+
+	return dt;
+}
+
 /**
  * unflatten_device_tree - create tree of device_nodes from flat blob
  *
@@ -1350,22 +1365,9 @@ void __init unflatten_device_tree(void)
  */
 void __init unflatten_and_copy_device_tree(void)
 {
-	int size;
-	void *dt;
-
-	if (!initial_boot_params) {
-		pr_warn("No valid device tree found, continuing without\n");
-		return;
-	}
+	if (initial_boot_params)
+		initial_boot_params = copy_device_tree(initial_boot_params);
 
-	size = fdt_totalsize(initial_boot_params);
-	dt = early_init_dt_alloc_memory_arch(size,
-					     roundup_pow_of_two(FDT_V17_SIZE));
-
-	if (dt) {
-		memcpy(dt, initial_boot_params, size);
-		initial_boot_params = dt;
-	}
 	unflatten_device_tree();
 }