mmc: am654_sdhci: Fix ITAPDLY for HS400 timing

At HS400 mode the ITAPDLY value is that from High Speed mode
which is incorrect and may cause boot failures.

The ITAPDLY for HS400 speed mode should be the same as ITAPDLY
as HS200 timing after tuning is executed. Add the functionality
to save ITAPDLY from HS200 tuning and save as HS400 ITAPDLY.

Fixes: c964447e ("mmc: am654_sdhci: Add support for input tap delay")
Signed-off-by: Judith Mendez <jm@ti.com>