KVM request types are normally defined using hex constants but QEMU traces
print decimal values instead, which is not very convenient.

This changes the request type format from %d to %x.
Signed-off-by: NAlexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: NAndreas Färber <afaerber@suse.de>
Reviewed-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>