When using -initrd in the virtio machine, we need to indicate the initrd
start and size inside the kernel image. These parameters need to be stored
in native endianness.

Signed-off-by: Alexander Graf <agraf@suse.de>
Acked-by: Richard Henderson <rth@twiddle.net>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>