KVM: PPC: ev_idle hcall support for e500 guests

Signed-off-by: Liu Yu <yu.liu@freescale.com>
[varun: 64-bit changes]
Signed-off-by: Varun Sethi <Varun.Sethi@freescale.com>
Signed-off-by: Stuart Yoder <stuart.yoder@freescale.com>
Signed-off-by: Alexander Graf <agraf@suse.de>