* for IMX8(M) the u-boot binary itself needs to be packed together with
the u-boot SPL binary, DDR firmware, SCU firmware and ATF firmware. For
this meta-freescale offers the imx-boot recipe.
* the imx-mkimage from Keith und Koep already includes some of the
firmwares pre-compiled, so these don't need to be built from source
* add a dynamic-layers structure to allow appending files only when
meta-freescale (freescale-layer) is present, so builds still work with
IMX6, where meta-freescale is not used
* use guf branch of u-boot-imx-kuk

BCS 746-000141