cpufreq: interactive: Rearm governor timer at max freq

Currently interactive governor timer doesn't re-arm itself when it
selects policy->max as the new frequency to go to. On hitting idle
for the first time at max frequency timer is armed again. This
mechanism doesn't have any noticeable performance benefits since
CPUs running at max frequencies without going into idles show high
loads which prevents the governor from lowering their frequencies.
This change rearms the timer even at max frequency which removes
the need to handle idle starts. This simplifies the code and also
makes the governor timer windows more regular so that the
notifications going out from the governor are uniformly spaced
apart. Max freq hysteresis start timestamp is refreshed everytime
policy->max is selected as the new frequency to prevent stepping
down from max frequency earlier than intended.

Change-Id: I9c137113b703f2064f1e668628db91de94cc0887
Signed-off-by: Rohit Gupta <rohgup@codeaurora.org>