cpufreq: Select PM_OPP rather than depending on it

cpufreq: Select PM_OPP rather than depending on it

PM_OPP is a helper library used by several of the existing cpufreq drivers.
Some of the drivers select this symbol while others depend on it and rely
on the architecture to enable it. Make this behaviour more consistent and
obvious by having all the drivers select the symbol. This will also allow
better build coverage of the affected drivers.

Signed-off-by: Mark Brown <broonie@linaro.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>