mmc: sdhci-omap: Add Support for Suspend/Resume

Add power management ops which save and restore the driver context and
facilitate a system suspend and resume.

Signed-off-by: Faiz Abbas <faiz_abbas@ti.com>
Link: https://lore.kernel.org/r/20200305151228.24692-1-faiz_abbas@ti.com


Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>