ANDROID: sched: Add vendor hook for uclamp_eff_get

Vendor may have their own behavior for determing uclamp value. Also
uclamp_eff_get() is used in uclamp_rq_inc_id() when task is enqueued,
and it is contained in uclamp_eff_value(), there is no much benefit to
hook uclamp_eff_value(), so remove the hook in uclamp_eff_value().

Bug: 170507972
Bug: 180859906
Signed-off-by: Rick Yiu <rickyiu@google.com>
Change-Id: Ibf7c043188a77c40baf5b4040b198a4197236089