opp: Add devm_pm_opp_attach_genpd

Add resource-managed version of dev_pm_opp_attach_genpd().

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
[ Viresh: Manually apply the patch and relocate the routines ]
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>