kvm: selftests: port dirty_log_test to aarch64

While we're messing with the code for the port and to support guest
page sizes that are less than the host page size, we also make some
code formatting cleanups and apply sync_global_to_guest().

Signed-off-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>