dt-bindings: pinctrl: at91: add sam9x7

Add device tree binding for SAM9X7 pin controller.

Signed-off-by: Varshini Rajendran <varshini.rajendran@microchip.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20240223172531.671993-1-varshini.rajendran@microchip.com


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>