cpus: protect work list with work_mutex Protect the list of queued work items with something other than the BQL, as a preparation for running the work items outside it. Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: KONRAD Frederic <fred.konrad@greensocs.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>