dt-bindings: pinctrl: pinctrl-microchip-sgpio: Fix indentation

yamllint warns:
./Documentation/devicetree/bindings/pinctrl/microchip,sparx5-sgpio.yaml
  102:10  error   wrong indentation: expected 10 but found 9 (indentation)
Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Link: https://lore.kernel.org/r/20210116015350.3501927-1-j.neuschaefer@gmx.netSigned-off-by: Linus Walleij <linus.walleij@linaro.org>