Integrate u-boot-seco-rk/seco_2017.09_next_develop_fit_ym

Commit: https://git.seco.com/edgehog/bsp/rockchip/u-boot-seco-rk/-/commit/5b90a8c0319bf37d71e1448ed709191c07d210a3

[FIT] Do not use external data when generating fit-dtb.blob

-E option is used to place data outside the FIT image (usually appended at the end of it). This works fine when the image is generated from a .its file, but without it (auto format), it causes problems. In particular, the scripts fail to compute correctly the data offset, causing the resulting FIT to be non-functional. We prefer to use embedded data instead.

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Commit: https://git.seco.com/edgehog/bsp/rockchip/u-boot-seco-rk/-/commit/51d260584808716164e02b9ac2d6683f98ccb7d5

[FIT] Improve DTB location in FIT

fdt_offset() looks for "data-offset" property inside the DTB node. This property can be absent when the FIT is generated without -E option (external data). In this case, DTB data is inside the FIT rather than appended to it. Using fit_image_get_data we can retrieve the DTB regardless of its position.

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Commit: https://git.seco.com/edgehog/bsp/rockchip/u-boot-seco-rk/-/commit/36b9ec750bf84e058949105635a1e5f31e6a0344

[FIT] Include multiple DTB blob inside FIT when using CONFIG_MULTI_DTB_FIT

Rockchip scripts for FIT node generation are used to generate u-boot.its; this file is then used to generate u-boot FIT image. When using CONFIG_MULTI_DTB_FIT we need to insert multiple DTB blob (fit-dtb.blob) in the place of u-boot.dtb. This blob is again a FIT image, containing all the possible DTBs for the board, listed in CONFIG_OF_LIST.