uboot-phytec

apalis_imx6: switch to zimage

Switch to the generic compressed Kernel image type (zImage) instead of
the U-Boot specific uImage format.

While at it also fix device tree naming for MMC DFU.

Signed-off-by: Bhuvanchandra DV <bhuvanchandra.dv@toradex.com>
Acked-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>