Add EV-iMX280-NANO-X-MB board

A simple prototyping board with one microSD port, one Ethernet port,
2 USB ports, I2C, SPI, GPIO, and UART interfaces.

Signed-off-by: Oleh Kravchenko <oleg@kaa.org.ua>
Cc: Stefano Babic <sbabic@denx.de>