Integrate u-boot-seco-imx/d18-dt-split

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Commit: https://git.seco.com/edgehog/bsp/nxp/u-boot-seco-imx/-/commit/995b6185b95c16685a630b321d186a1f6e6abb40

[ALL] add default carrier overlay configuration support

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Commit: https://git.seco.com/edgehog/bsp/nxp/u-boot-seco-imx/-/commit/f5fcaf98d51e741179f5e2565ac67ad820c31a87

[ALL] remove unused var DEFAULT_OVERLAY_FILE

conf/SRCREV.conf

 SRCREV:pn-imx-mkimage = "088ceee66994ace0d9c296170ec51b8c7935f84d"
-SRCREV:pn-u-boot-seco-imx = "92e9d0ca5db882ab2721997d75f07c3a6989f93f"
+SRCREV:pn-u-boot-seco-imx = "995b6185b95c16685a630b321d186a1f6e6abb40"
 SRCREV:pn-linux-seco-imx = "5c4e4a271f1e69f1857859473957f236cf9f4805"
 SRCREV:pn-u-boot-seconorth-imx = "7477fa0a389942cee3d2e275096989a69f0382f9"
 SRCREV:pn-linux-seconorth-imx = "104f5abdd4e7933fd4b795c52e1adf49430aff60"