cpufreq: interactive: marry governor boostpulse with auto_hotplug boostpulse.

Limit boosted cores to 2 since that matches with what auto_hotplug boostpulse brings online. We will boost no more than 2 cores.

Ref: https://github.com/motley-git/kernel-Nexus4/commit/009f418681e3df86ebcbad08b967d08178217f5d