Integrate u-boot-seco-imx/seco_lf_v2021.04-gm_mx8qm_docs
[C26] remove NXP README
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[C26] fix Kconfig target description
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[C43] update MAINTAINERS
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[C43] fix Kconfig target description
[C26] remove NXP README
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[C26] fix Kconfig target description
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[C43] update MAINTAINERS
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[C43] fix Kconfig target description