cpufreq: interactive: Add check_fast mode to raise freqs faster

It takes too long to scale from min_freq to max_freq. If you ignore
go_hispeed, then it takes over 100ms to step up through all the
frequencies. Even with go_hispeed, I think I figured it was 90ms to go
from idle to max speed.

The core of the problem is that a cpu_load << 100% is meaningful for
scaling.  As that load approaches 100% though, this estimate becomes
meaningless.

Here "meaningful" means that the speed adjusted load is a good approximation
of the total processing work needed and therefore good for estimating the
target frequency.

At 100% it is not meaningful because either it is a perfect estimate (had
we been running faster there is no more work we would have done) or off by
a factor of max_freq/min_freq in the worst case.

This patch recognizes this case and scales more aggressively.  At the same
time it also re-estimates in a shorter time to correct over/under scaling.

Change-Id: I0b199f3aa9f451cf500ec3c73ef3352f1661b0c0