arm64: defconfig: Enable imx8mm clk/pinctrl

Basic imx8mm support is already available in linux-next just not
enabled in arm64 defconfig. With this patch imx8mm-evk can boot.

Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
Reviewed-by: Dong Aisheng <aisheng.dong@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>