pinctrl: imx8m: kconfig: Depends on SOC_IMX8M

Change PINCTRL_IMX8M* dependency from just ARCH_MXC to SOC_IMX8M,
likewise is done for other PINCTRL_IMX* kconfig. This avoid polluting
the config when SOC_IMX8M is not enabled.

Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Link: https://lore.kernel.org/r/20220830142727.313080-1-francesco.dolcini@toradex.com


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