arm: mach-kirkwood: convert to use mvebu-mbus driver

This commit migrates the mach-kirkwood platforms to use the mvebu-mbus
driver and therefore removes the Kirkwood-specific addr-map code.

The kirkwood_init_early() function is now responsible for initializing
the mvebu-mbus driver by calling mvebu_mbus_init().

The address decoding windows are now registered in the
kirkwood_setup_wins() function. It is worth noting that the four PCIe
address decoding windows will ultimately no longer have to be
registered here: it will be done automatically by the PCIe driver once
Kirkwood has been migrated to use the upcoming mvebu PCIe driver.

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