arm: dra7xx: Add board files for DRA7XX socs

Adding new board files for DRA7XX socs.
The pad registers layout is changed completely from OMAP5
So introducing the new structure here and also adding the
minimal data.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Signed-off-by: Nishant Kamat <nskamat@ti.com>
Signed-off-by: R Sricharan <r.sricharan@ti.com>
Reviewed-by: Tom Rini <trini@ti.com>
[trini: Adapt omap_mmc_init call for last 2 params]
Signed-off-by: Tom Rini <trini@ti.com>