bsh: imx6ulz_smm_m2: Add imx6ulz BSH SMM M2 boards

Introduce BSH SystemMaster (SMM) M2 board family, which consists of:
imx6ulz SMM M2 and imx6ulz SMM M2 PRO boards.

Add support for imx6ulz BSH SMM M2 board:

- 128 MiB DDR3 RAM
- 256MiB Nand
- USBOTG1 peripheral - fastboot.

Signed-off-by: Michael Trimarchi <michael@amarulasolutions.com>
Reviewed-by: Fabio Estevam <festevam@denx.de>