of: overlay: Fix function name disparity

Fixes the following W=1 kernel build warning(s):

 drivers/of/overlay.c:147: warning: expecting prototype for of_overlay_notifier_register(). Prototype was for of_overlay_notifier_unregister() instead

Cc: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
Cc: Frank Rowand <frowand.list@gmail.com>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: devicetree@vger.kernel.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210318104036.3175910-10-lee.jones@linaro.org

drivers/of/overlay.c

@@ -140,7 +140,7 @@ int of_overlay_notifier_register(struct notifier_block *nb)
 EXPORT_SYMBOL_GPL(of_overlay_notifier_register);
 
 /**
- * of_overlay_notifier_register() - Unregister notifier for overlay operations
+ * of_overlay_notifier_unregister() - Unregister notifier for overlay operations
  * @nb:		Notifier block to unregister
  */
 int of_overlay_notifier_unregister(struct notifier_block *nb)