mmc: am654_sdhci: Update output tap delay writes

With the latest RIOT, there is a different otap delay value for each
speed mode. Add a new binding with every supported speed mode. Also
disable a given speed mode in the host caps if its corresponding
otap-del-sel is not present.

Signed-off-by: Faiz Abbas <faiz_abbas@ti.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>