ARM: orion5x: fix mvebu_mbus_dt_init call

The prototype for mvebu_mbus_dt_init() changed around the same time
as a new caller was added to orion5x. This adds the missing argument
to make orion5x behave correctly.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>