sched: fair: remove nr_running=1 restriction for sync wakeups

Currently, the sync wakeup is honored only if waker was the single
task running on the cpu. More often, the waker is sharing the cpu
along with other tasks and with this check the wakee is pushed
to a different cpu. This causes regression in some performance
sensitive usecases.

Remove this change.

CRs-Fixed: 2360960
Change-Id: Idb961bd7333be891d3643da73473c3182710876b
Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>