mmc: host: Update HS400 timing mode before performing tuning

Updating HS400 timing mode, before performing tuning.
Timing should be adjusted to the HS400 target operation
frequency for tuning process. Similar handling is also
done in mmc_hs200_tuning(). This is handled properly in
sdhci-msm.c from msm-5.4 onwards.

Change-Id: I39ec61033843b90bb178756e2910419fafafa78a
Signed-off-by: Sridhar Arra <sarra@codeaurora.org>