sunxi: Enable SMP mode for the boot CPU on sun9i (A80)

Since the A80 has many cores which we intend to use in SMP fashion,
we should set the SMP bit for the boot CPU.

[wens@csie.org: Added commit message]
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>