Add initial support for Technexion's PICO-IMX6UL-EMMC board

Add support for Technexion's PICO-IMX6UL-EMMC board.

For information about this board, please visit:
http://www.technexion.com/products/pico/pico-som/pico-imx6-emmc



Signed-off-by: Richard Hu <richard.hu@technexion.com>
Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>