of: overlay: Fix trivial typo

Permitted is spelled with two t.

Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Link: https://lore.kernel.org/r/20221220-permited-v1-3-52ea9857fa61@chromium.org


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