QEMU does have an I/O thread now, that can be interrupted at any time
because the VCPU thread runs outside the iothread mutex.

Therefore, the kvmppc_timer_hack is obsolete.  Remove it.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NAlexander Graf <agraf@suse.de>