Add the basic dts file for i.MX8ULP EVK board.
Only the necessary devices for minimal system boot up are enabled:
enet, emmc, usb, console uart.

some of the devices' pin status may lost during low power mode,
so additional sleep pinctrl properties are included by default.
Reviewed-by: Dong Aisheng <aisheng.dong@nxp.com>
Signed-off-by: Jacky Bai <ping.bai@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>