dt-bindings: pinctrl: imx: Support i.MX91 IOMUXC

i.MX91 and i.MX93 share similar design. They could share same dt-binding
doc, so rename fsl,imx93-pinctrl.yaml to fsl,imx9-pinctrl.yaml and add
i.MX91 compatible string

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20240513-imx91-pinctrl-v1-1-c99a23c6843a@nxp.com


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