This adds a defconfig for sama5d27_som1_ek board to get environment from
uSD. The defconfig is made from sama5d27_som1_ek_mmc_defconfig, with
'bootcmd' and 'bootargs' changed to kernel, device-tree and rootfs from
uSD. The environment is expected to be found in uSD's FAT partition.
Signed-off-by: Codrin Ciubotariu <codrin.ciubotariu@microchip.com>
