cpufreq: schedutil: Update hispeed load condition

Checking the utilization against current capacity can cause the hispeed
load condition to be unreliable. This can happen if the hispeed condition
is reevaluated after some other event (say, migration) causes the current
frequency (and thereby current capacity) to change.

So, instead of checking against current capacity, check against the average
capacity that is less temperamental.

Change-Id: Ic1277908f7d42848ded5dd450146d1d04572eaab
Signed-off-by: Saravana Kannan <skannan@codeaurora.org>