update_kernel: Enable hypervisor boot support on ARM

We already have --[no]hv for x86, just adding an effect of that flag for
ARM as well.

BUG=b:145357269
TEST=tested with some cheza64/trogdor CLs for ManaTEE

Change-Id: I7318f48b9832956c31a06fd6555a93348939e33e
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosutils/+/2401963
Tested-by: Micah Morton <mortonm@chromium.org>
Reviewed-by: Tomasz Jeznach <tjeznach@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>