ARM: mvebu: Add Device Bus support for Armada 370/XP SoC

Armada 370 and Armada XP SoC have a Device Bus controller to
handle NOR, NAND, SRAM and FPGA devices.
This patch adds the device tree node to enable the controller.

Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>