dt-bindings: pinctrl: ocelot: Add LAN9645x SoC support

dt-bindings: pinctrl: ocelot: Add LAN9645x SoC support

Add documentation for the compatibles designated for the following SKUs
in the LAN9645x family:

lan96455f
lan96457f
lan96459f

with fallback a compatible for the smallest 5-ported SKUs lan96455f.

Reviewed-by: Steen Hegelund <Steen.Hegelund@microchip.com>
Reviewed-by: Daniel Machon <daniel.machon@microchip.com>
Signed-off-by: Jens Emil Schulz Østergaard <jensemil.schulzostergaard@microchip.com>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Linus Walleij <linusw@kernel.org>