mmc: tegra: add sdhci tegra suspend and resume

This patch adds suspend and resume PM ops for tegra SDHCI.

Acked-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Sowjanya Komatineni <skomatineni@nvidia.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>