cpufreq: Add a boostpulse interface to ondemand

For applications that require a one-shot increase in frequency,
the boostpulse interface would help to scale to max for the time
specified in boostime. This helps applications that currently
increases scaling_min_freq and resets later after a fixed duration.
Instead of changing scaling_min_freq applications can directly write
to boostpulse and governer resets during regular timer after the time
expires.

Change-Id: Ie5f490ff06b41364aa76dd468573433495da28a4
Signed-off-by: Narayanan Gopalakrishnan <nargop@codeaurora.org>