arm: i.MX6UL: add Armadeus Systems OPOS6UL SoM and OPOS6ULDev carrier board

OPOS6UL is an i.MX6UL based SoM with 256MB RAM, 4GB eMMC and an ethernet
phy. OPOS6ULDev is carrier board for the OPOS6UL.

U-Boot SPL 2017.03-rc3-00002-g5085c26 (Mar 07 2017 - 09:48:09)
Trying to boot from MMC1

U-Boot 2017.03-rc3-00002-g5085c26 (Mar 07 2017 - 09:48:09 +0100)

CPU:   Freescale i.MX6UL rev1.0 528 MHz (running at 396 MHz)
CPU:   Industrial temperature grade (-40C to 105C) at 40C
Reset cause: POR
Model: Armadeus Systems OPOS6UL SoM on OPOS6ULDev board
DRAM:  256 MiB
MMC:   FSL_SDHC: 0, FSL_SDHC: 1
Video: 800x480x18
In:    serial
Out:   serial
Err:   serial
Net:   FEC [PRIME]
Hit any key to stop autoboot:  0

Signed-off-by: Sébastien Szymanski <sebastien.szymanski@armadeus.com>
Reviewed-by: Simon Glass <sjg@chromium.org>