arm: mvebu: Remove legacy U-Boot header from kwbimage v1 files

arm: mvebu: Remove legacy U-Boot header from kwbimage v1 files

The SPL code now already parses kwbimage v1 headers where all necessary
information about how to load and execute U-Boot proper is present. The
legacy 64-byte U-Boot header is not used anymore.

Remove this 64-byte header by putting u-boot.bin binary (instead of
u-boot.img) into kwbimage v1 and let SPL code or BootROM to load U-Boot
directly at its execution address.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Chris Packham <judge.packham@gmail.com>
Reviewed-by: Stefan Roese <sr@denx.de>