of: Documentation: Fix forgotten reference to of_overlay_apply()

Fixes: 93a6039000 ("of: Documentation: of_overlay_apply() replaced by of_overlay_fdt_apply()")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/overlay-notes.txt

@@ -91,8 +91,8 @@ The API is quite easy to use.
 return value is an error or a cookie identifying this overlay.
 
 2. Call of_overlay_remove() to remove and cleanup the overlay changeset
-previously created via the call to of_overlay_apply(). Removal of an overlay
+previously created via the call to of_overlay_fdt_apply(). Removal of an
-changeset that is stacked by another will not be permitted.
+overlay changeset that is stacked by another will not be permitted.
 
 Finally, if you need to remove all overlays in one-go, just call
 of_overlay_remove_all() which will remove every single one in the correct