This patch gives U-boot the runtime support to have the board specific
code decide which FDT to use. This is especially useful for devices
that need this type of runtime determination and also doesn't use SPL.

Signed-off-by: Franklin S Cooper Jr <fcooper@ti.com>
Reviewed-by: Lokesh Vutla <lokeshvutla@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>