pinctrl: freescale: Break dependency on SOC_IMX8MQ for i.MX8MQ

The CONFIG_SOC_IMX8MQ will go away, so the dependency can be based on
ARCH_MXC && ARM64.

Signed-off-by: Abel Vesa <abel.vesa@nxp.com>
Acked-by: Dong Aisheng <aisheng.dong@nxp.com>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>