arm: mach-mv78xx0: convert to use the mvebu-mbus driver

This commit convers the mach-mv78xx0 sub-architecture to use the
mvebu-mbus driver. We simply have to call mvebu_mbus_init() in the
->init_early() function, and modify the PCIe code so that it uses the
new functions provided by mvebu-mbus to create the needed PCIe
windows.

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