[core/sched/cbs] Add KConfig defined options for CBS

This KConfig option allows to enable CBS scheduler as well as to setup
some of its parameters. For the time being, we defined via KConfig just
the TQ value in [ns]. Such a definition is required to perform [ns] to [tq]
conversion in the ftrace source as well.

Signed-off-by: Patrick Bellasi <derkling@gmail.com>
[core/sched/cbs] Use KConfig defined TQ value

Signed-off-by: Patrick Bellasi <derkling@gmail.com>
[core/sched/cbs] Dump all FTrace timing in TQ units

This should improve trace readability while still keeping the necessary
resolution to evaluate scheduler performances.

Signed-off-by: Patrick Bellasi <derkling@gmail.com>
[core/sched/cbs] Bugfix burst uppwer/lower bound units

The Upper and Lover bound of a burst are defined in [ns] units but are
expected to be in [TQ] units by the control model. This patch add the
conversion before the actual factor multiplication.

Signed-off-by: Patrick Bellasi <derkling@gmail.com>
[core/sched/cbs] Bugfix RoundTime SP update

The SP for a round time should be updated _after_ the round error of the
previous run has been computed but _before_ the round event is traced via
ftrace, since such event should report the SP for the _next_ round.

This patch move the SP update into the round tuning function, right before
the next round event is going to be traced via FTrace.

Signed-off-by: Patrick Bellasi <derkling@gmail.com>
[core/sched/cbs] Inline round tuning function

The round setup function is now so simple that it makes no more sense to
keep it apart. Let's inline it for the time being.

Signed-off-by: Patrick Bellasi <derkling@gmail.com>