of: overlay: unittest: overlay_bad_unresolved: Spelling s/ok/okay/

While "ok" is recognized, the proper status value for an operational
device is "okay".

Fixes: eb38b952 ("of: overlay: unittest: Add test for unresolved symbol")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/923f4f605b86f23d001c6efc9c2237ab449d447d.1698228277.git.geert+renesas@glider.beSigned-off-by: Rob Herring <robh@kernel.org>

drivers/of/unittest-data/overlay_bad_unresolved.dtso

@@ -3,5 +3,5 @@
 /plugin/;
 
 &this_label_does_not_exist {
-	status = "ok";
+	status = "okay";
 };