exec: Do vmstate unregistration from cpu_exec_exit()
cpu_exec_init() does vmstate_register for the CPU device. This needs to be
undone from cpu_exec_exit(). This change is needed to support CPU hot
removal.
Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com> Reviewed-by: Thomas Huth <thuth@redhat.com> Reviewed-by: David Gibson <david@gibson.dropbear.id.au> Acked-by: Paolo Bonzini <pbonzini@redhat.com>
[dwg: added missing include to fix compile on some archs] Signed-off-by: David Gibson <david@gibson.dropbear.id.au>