mmc: sdhci-of-esdhc: add tuning support

eSDHC uses tuning block for tuning procedure. So the tuning
block control register must be configured properly before tuning.

Signed-off-by: Yangbo Lu <yangbo.lu@nxp.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>