hw/xen: use correct default protocol for xen-block on x86

Even on x86_64 the default protocol is the x86-32 one if the guest doesn't
specifically ask for x86-64.

Cc: qemu-stable@nongnu.org
Fixes: b6af8926fb85 ("xen: add implementations of xen-block connect and disconnect functions...")
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
1 file changed