of: overlay: enable of_overlay_fdt_apply() kerneldoc

of_overlay_fdt_apply() already has a kerneldoc-formatted documentation,
except it is nor marked as such. Adding the second asterisk is enough for
the documentation to take it into account correctly.

Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20231106-of_overlay_fdt_apply-kerneldoc-v1-1-9a2d132bc6c1@bootlin.com


Signed-off-by: Rob Herring <robh@kernel.org>