Revert "rcu: Make RCU_FAST_NO_HZ take advantage of numbered callbacks"

This reverts commit c0f4dfd4.

The above change allows the CPU to enter idle with RCU callbacks pending
for the durations specified in rcu_idle_gp_delay or rcu_idle_lazy_gp_delay.
This was causing a throughput decrease in synchronize_rcu(), as mentioned
by the original author.
These decreases were determined to be too large, as sub- 1 jiffy
synchronize_rcu() latency in cpu idle scenarios was desired.

Reverting this change change in order to start the force_quiescent_state()
state machine upon entering idle, rather than on the scheduler tick()

CRs-Fixed: 887035
Change-Id: I61865131dad751ec0fa14653b2b08b8bada4d061
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>