Integrate meta-seco-imx/u-boot-seco-imx/seco_lf_v2021.04_develop_c72n_ym

Commit: edgehog/layers/seco/meta-seco-imx@60e861f2

Integrate u-boot-seco-imx/seco_lf_v2021.04_develop_c72n_ym

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Commit: edgehog/bsp/nxp/u-boot-seco-imx@0e6729a6

[C72n][SPL][DEFCONFIG] enable boot from eMMC

fix bug when trying to boot from eMMC:

mmc_load_image_raw_sector: mmc block read error SPL: failed to boot from all boot devices ### ERROR ### Please RESET the board ###

• delete raw sector correction (derived from evk, not valid on our board)
• enable mmc usage at SPL