scheduler: compute time-average nr_running per run-queue

Compute the time-average number of running tasks per run-queue for a
trailing window of a fixed time period. The detla add/sub to the
average value is weighted by the amount of time per nr_running value
relative to the total measurement period.

Change-Id: I4b1fa8fee82a549889560ceded4b94bdb811671d
Signed-off-by: Diwakar Tundlam <dtundlam@nvidia.com>
Reviewed-on: http://git-master/r/108070
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Ryan Wong <ryanw@nvidia.com>
Tested-by: Ryan Wong <ryanw@nvidia.com>
tcp: Proportional Rate Reduction for TCP

credits to faux123

Change-Id: I776dab4b2306bdfef9c34f57d3b83df7b7f627a7