sched: sched_avg: Fix sched_get_nr_running_avg for tri-cluster systems

sched_get_nr_running_avg() sets values for the various arguments
passed to it and one of them is max number of tasks running
on the max capacity CPUs which breaks tri-cluster systems.
Fix it by updating condition by checking for CPUs other than min
capacity CPUs.

Change-Id: I3f519a7fd1ee89796818e03967abe77f9a72cbb8
Signed-off-by: Satya Durga Srinivasu Prabhala <satyap@codeaurora.org>