cpufreq: interactive: Optimize sync_freq implementation

Don't let frequency drop below sync_freq if either load or
frequency among other cpus is above a certain threshold,
not necessarily both.

Change-Id: Iada28e08e812498e16d5189b309a7314f88814dd
cpufreq: interactive: Add limits_changed to boosted case
cpufreq: interactive: Honor changed minimum frequency

This saves a few cycles in the timer routine.
cpufreq: interactive: Use parts of native boost routine

Not all governors are created equal. Set boostpulse_endtime
and floor_freq to smoothen the timer routine.