MLK-16499-1 mmc: Add support for HS400

The HS400 ES (Enhanced Strobe) has been added. This patch addes support
for HS400 for eMMC 5.0 devices. It needs tuning at HS200 to synchronize
command response.

Signed-off-by: Ye Li <ye.li@nxp.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Troy Kisky <troy.kisky@boundarydevices.com>