mmc: sdhci-msm: Add pm_runtime and system PM support

Provides runtime PM callbacks to enable and disable clock resources
when idle. Also support system PM callbacks to be called during system
suspend and resume.

Reviewed-by: Ritesh Harjani <riteshh@codeaurora.org>
Reviewed-by: Georgi Djakov <georgi.djakov@linaro.org>
Tested-by: Ritesh Harjani <riteshh@codeaurora.org>
Signed-off-by: Pramod Gurav <pramod.gurav@linaro.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>