automation: Switch arm32 cross builds to run on arm64

automation: Switch arm32 cross builds to run on arm64

Due to the limited x86 CI resources slowing down the whole pipeline,
switch the arm32 cross builds to be executed on arm64 which is much more
capable. For that, rename the existing debian container dockerfile
from unstable-arm32-gcc to unstable-arm64v8-arm32-gcc and use
arm64v8/debian:unstable as an image. Note, that we cannot use the same
container name as we have to keep the backwards compatibility.
Take the opportunity to remove extra empty line at the end of a file.

Modify the tag of .arm32-cross-build-tmpl to arm64 and update the build
jobs accordingly.

Signed-off-by: Michal Orzel <michal.orzel@amd.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>