cpufreq: Interactive: Implement per policy instances of governor

If we have a multi-package system, where we have multiple instances of struct
policy (per package), currently we can't have multiple instances of same
governor. i.e. We can't have multiple instances of Interactive governor for
multiple packages.

This is a bottleneck for multicluster system, where we want different packages
to use Interactive governor, but with different tunables.

This patch uses the infrastructure provided by earlier patches pushed in
Mainline in v3.10-rc1/rc2 and implements per policy instances of Interactive
governor.

Change-Id: I70436d4a5a45c6cb6edf37f3e46d0b9fbc930982
[toddpoynor@google.com: merge with later code, minor changes]
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>