Init the itc_offset for all possible vCPUs. The current code by
mistake ends up only initializing the offset on vCPU 0.

Spotted by Gleb Natapov.
Signed-off-by: Jes Sorensen <jes@sgi.com>
Acked-by : Xiantao Zhang <xiantao.zhang@intel.com>
Signed-off-by: Avi Kivity <avi@redhat.com>