imx8mq: Enable eMMC HS400 and SD UHS mode on EVK

imx8mq: Enable eMMC HS400 and SD UHS mode on EVK

iMX8MQ EVK board has a eMMC5.0 chip and supports SD3.0, so enable the UHS
and HS400 configs to enhance the eMMC/SD access.

The change also needs to set usdhc clock to 400Mhz, and add the
off-on-delay-us to SD reset pin, otherwise some SD cards will
fail to select UHS mode in re-initialization.

Reviewed-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Ye Li <ye.li@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>