imx: kontron-sl-mx8mm: Enable environment in MMC

In case we boot from SD card or eMMC, we also want to load
the environment from the according boot device.

Signed-off-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Reviewed-by: Fabio Estevam <festevam@denx.de>
2 files changed