arm/arm64: Move setup_vm into setup

Consolidate our setup calls to reduce the amount we need to do from
init::start. Also remove a couple of pointless comments from setup().

Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com>
Tested-by: Alexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: Andrew Jones <drjones@redhat.com>