Integrate meta-seconorth-machine/mx6_fix_vpu_install_task

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Commit: seco-ne/yocto/layers/meta-seconorth-machine@aeb1509b

conf:seco-mx6-fsl: Add mx6dl to MACHINEOVERRIDES

The VPU firmware binary for the imx6dl SoCs was not present in the
image. Adding the mx6dl override adds the firmware-imx-vpu-imx6d package
to the image.

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Commit: seco-ne/yocto/layers/meta-seconorth-machine@5afddac3

kernel:firmware: Fix install task for seco-mx6-fsl sdk build

Perform the do_install task only for the seco-mx6 machines, otherwise the
firmware binaries conflict with the files from the firmware-imx recipe
of the Freescale layer.