KVM: ia64: fix sparse warnings

This patch fixes some sparse warning about "dubious one-bit signed bitfield."

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Originally-by: Jan Blunck <jblunck@suse.de>
Signed-off-by: Jan Blunck <jblunck@suse.de>
Acked-by: Xiantao Zhang <xiantao.zhang@intel.com>
Signed-off-by: Avi Kivity <avi@redhat.com>