Add support for the Secure Digital Host Controller Interface (SDHCI)
present on TI's AM654 SOCs. It is compatible with eMMC5.1 Host
Specifications.

Enable only upto HS200 speed mode.
Signed-off-by: Faiz Abbas <faiz_abbas@ti.com>
Acked-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Tero Kristo <t-kristo@ti.com>