cpufreq: interactive: Revert timer start modification

commit f8b27656
(cpufreq: Sync on thread migration optimizations)
introduced a change to cpufreq_interactive_timer_start() in order
to reschedule the timer differently based on whether min or max
is changed. A better way is to reschedule the timer only when
necessary.

Revert timer start modification in preparation for the final fix.

Change-Id: I13f3b75a6eee03ac6380c24db899806a9bfbc96a
Signed-off-by: Junjie Wu <junjiew@codeaurora.org>