workqueue: swap set_cpus_allowed_ptr() and PF_NO_SETAFFINITY

Move the setting of PF_NO_SETAFFINITY up before set_cpus_allowed()
in create_worker(). Otherwise userland can change ->cpus_allowed
in between.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>