sched/deadline: Add basic HMP extensions

Some HMP extensions have to be supported by all scheduling classes
irrespective of them using HMP task placement or not. Add these
basic extensions to make deadline scheduling work.

Also during the tick, if a deadline task gets throttled, its HMP
stats get decremented as part of the dequeue. However, the throttled
task does not update its on_rq flag causing HMP stats to be double
decremented when update_history() is called as part of a window rollover.
Avoid this by checking for throttled deadline tasks before subtracting
and adding the deadline tasks load from the rq cumulative runnable avg.

Change-Id: I9e2ed6675a730f2ec830f764f911e71c00a7d87a
Signed-off-by: Syed Rameez Mustafa <rameezmustafa@codeaurora.org>