of: unittest: fix memory leak in attach_node_and_children

In attach_node_and_children memory is allocated for full_name via
kasprintf. If the condition of the 1st if is not met the function
returns early without freeing the memory. Add a kfree() to fix that.

This has been detected with kmemleak:
Link: https://bugzilla.kernel.org/show_bug.cgi?id=205327

It looks like the leak was introduced by this commit:
Fixes: 5babefb7f7 ("of: unittest: allow base devicetree to have symbol metadata")

Signed-off-by: Erhard Furtner <erhard_f@mailbox.org>
Reviewed-by: Michael Ellerman <mpe@ellerman.id.au>
Reviewed-by: Tyrel Datwyler <tyreld@linux.ibm.com>
Signed-off-by: Rob Herring <robh@kernel.org>

drivers/of/unittest.c

@@ -1236,8 +1236,10 @@ static void attach_node_and_children(struct device_node *np)
 	full_name = kasprintf(GFP_KERNEL, "%pOF", np);
 
 	if (!strcmp(full_name, "/__local_fixups__") ||
-	    !strcmp(full_name, "/__fixups__"))
+	    !strcmp(full_name, "/__fixups__")) {
+		kfree(full_name);
 		return;
+	}
 
 	dup = of_find_node_by_path(full_name);
 	kfree(full_name);