This patch adds a small binary kernel to test aarch64 virt machine's
UART.

Signed-off-by: Wei Huang <wei@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[thuth: Fixed contextual conflicts with the hppa and sdhci patches]
Signed-off-by: Thomas Huth <thuth@redhat.com>