This imports the Marvell mbus driver from Linux. The mbus is the
main downstream bus found on all Marvell Orion SoCs. The driver
deals with re-configurable address windows which are currently
parsed from DT. Also enable the driver as default on all MVEBU
SoCs. While at it, also reorder drivers/bus/{Kconfig,Makefile}
alphabetically.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>