arm64:Add support for building uImage

commit 007b0bba from
https://github.com/axxia/linux-yocto.git

 v5.10/standard/axxia-dev/base.

Enable building uImage for arm64.

Signed-off-by: Jiang Lu <lu.jiang@windriver.com>
Signed-off-by: Yanjiang Jin <yanjiang.jin@windriver.com>
Signed-off-by: Liwei Song <liwei.song@windriver.com>