configs/imx6dlsabreauto: Use zImage by default
Currently the generated sdcard.img does not boot because U-Boot looks for
a zImage type of kernel instead of uImage.
Remove the generation of uImage, so that the sdcard.img can successfully
boot.
Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>