mmc: sdhci-msm: Convert to use resource-managed OPP API

Use resource-managed OPP API to simplify code.

Signed-off-by: Yangtao Li <tiny.windzz@gmail.com>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>