of: Documentation: of_overlay_apply() replaced by of_overlay_fdt_apply()

Signed-off-by: Frank Rowand <frank.rowand@sony.com>

Documentation/devicetree/overlay-notes.txt

@@ -87,8 +87,8 @@ Overlay in-kernel API
 
 The API is quite easy to use.
 
-1. Call of_overlay_apply() to create and apply an overlay changeset. The return
-value is an error or a cookie identifying this overlay.
+1. Call of_overlay_fdt_apply() to create and apply an overlay changeset. The
+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