pinctrl: imx8mn: Constify imx_pinctrl_soc_info

The imx_pinctrl_soc_info structure content is never changed, so it can be
declared as 'const', like it is done on all other i.MX pinctrl drivers.

Make it 'const' in this driver too.
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Reviewed-by: Dong Aisheng <aisheng.dong@nxp.com>
Link: https://lore.kernel.org/r/20210713122513.3112941-1-festevam@gmail.comSigned-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/freescale/pinctrl-imx8mn.c

@@ -317,7 +317,7 @@ static const struct pinctrl_pin_desc imx8mn_pinctrl_pads[] = {
 	IMX_PINCTRL_PIN(MX8MN_IOMUXC_UART4_TXD),
 };
 
-static struct imx_pinctrl_soc_info imx8mn_pinctrl_info = {
+static const struct imx_pinctrl_soc_info imx8mn_pinctrl_info = {
 	.pins = imx8mn_pinctrl_pads,
 	.npins = ARRAY_SIZE(imx8mn_pinctrl_pads),
 	.gpr_compatible = "fsl,imx8mn-iomuxc-gpr",