imx: support for conga-QMX8 board

Add i.MX8QM qmx8 congatec board support

U-Boot 2021.07-rc3-00528-gc9a966d9dd (May 31 2021 - 15:21:25 +0200)

CPU:   NXP i.MX8QM RevB A53 at 1200 MHz

Model: Congatec QMX8 Qseven series
Board: conga-QMX8
Build: SCFW 494c97f3, SECO-FW d63fdb21, ATF 09c5cc9
Boot:  SD2
DRAM:  6 GiB
MMC:   FSL_SDHC: 0, FSL_SDHC: 1, FSL_SDHC: 2
Loading Environment from MMC... OK
In:    serial@5a060000
Out:   serial@5a060000
Err:   serial@5a060000
switch to partitions #0, OK
mmc2 is current device
Net:
Error: ethernet@5b040000 address not set.
No ethernet found.

Hit any key to stop autoboot:  0

Signed-off-by: Oliver Graute <oliver.graute@kococonnector.com>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: Peng Fan <peng.fan@nxp.com>
Cc: Simon Glass <sjg@chromium.org>
Cc: Ye Li <ye.li@nxp.com>
Cc: uboot-imx <uboot-imx@nxp.com>