Add TI814X EVM board directory, config file, and MAINTAINERS
entry. Enable build.

Signed-off-by: Matt Porter <mporter@ti.com>
Reviewed-by: Tom Rini <trini@ti.com>
[trini: Adapt to recent omap_hsmmc requirements, Matt re-tested]
Signed-off-by: Tom Rini <trini@ti.com>