ARM: OMAP2+: board-generic: add support for DRA71x family

DRA71x processor family is a derivative of DRA722 ES2.0 targetted for
infotainment systems.

Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>