Integrate u-boot-seco-imx/seco_lf_v2021.04_develop_myon2-imx8mm-video-list

Commit: clea-os/bsp/nxp/u-boot-seco-imx@657a84eb

[IMX8MM][MYON2] use video_mode_list to select display overlay

Selection of device tree overlay for display should be available via "seco_config video" and not via "seco_config peripheral".