arm64: sunxi: adjust default load addresses

As arm64 has slightly different expectations about load addresses, lets
use a different set of default addresses for things like the kernel.
As arm64 kernels don't come with a decompressor right now, reserve some
more space for really big uncompressed kernels.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>