microblaze: Enable REMAKE_ELF

microblaze: Enable REMAKE_ELF

Enable u-boot.elf recreation from u-boot.bin to prepare for removing manul
relocation. Enable option for big endian configuration but it is not used
too much that's why it is completely untested.
By supporting this system there is a need to define LITTLE/BIG endian
Kconfig options to pass -EL/-EB flags.

Full command line for u-boot.elf recreation looks like this:
microblazeel-xilinx-linux-gnu-objcopy -I binary -B microblaze \
 -O elf32-microblazeel u-boot.bin u-boot-elf.o

Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/7e242a519fcd1c693b9103c5599b515af555ca43.1655299267.git.michal.simek@amd.com