cpu-boost: Rework scheduling setup

This patch minimizes the latency of an input
boost by creating a dedicated kworker and scheduling
it with the realtime policy "SCHED_FIFO".
We use "MAX_RT_PRIO - 2" to have the input
boost task preempt userspace RT tasks
if needed while being preempted by kernel
internal RT tasks which are scheduled at
"MAX_RT_PRIO - 1" or higher.

Also since now the cpu-boost wq would
only handle the work to disable a running
input boost, which isn't latency critical,
we break up the cpu-boost wq and move the
work to disable a running input boost
to the shared regular wq.

[Changed kthread method names for 4.9 kernel.]

Change-Id: I846cc5d6f7143cff2f3318aefba5f2d9ed65b86d
3 files changed