mmc: sdhci-msm: Save the calculated tuning phase

Save the tuning phase once the tuning is performed.
This phase value will be used while calibrating DLL
for HS400 mode.

Signed-off-by: Ritesh Harjani <riteshh@codeaurora.org>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>