workqueue: Shorten events_freezable_power_efficient name

Since we have set the WQ_NAME_LEN to 32, decrease the name of
events_freezable_power_efficient so that it does not trip the name length
warning when the workqueue is created.

Signed-off-by: Audra Mitchell <audra@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>