dt-bindings: phy: renesas: usb3-phy: Spelling s/funcional/functional/

Fix a misspelling of the word "functional".

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Link: https://lore.kernel.org/r/3da9bd360e1c83007af0e0e90fa4e6c2b50fdab3.1652100633.git.geert+renesas@glider.be


Signed-off-by: Vinod Koul <vkoul@kernel.org>