bus: mvebu-mbus: allow several windows with the same target/attribute

bus: mvebu-mbus: allow several windows with the same target/attribute

Having multiple windows with the same target and attribute is actually
legal, and can be useful for PCIe windows, when PCIe BARs have a size
that isn't a power of two, and we therefore need to create several
MBus windows to cover the PCIe BAR for a given PCIe interface.

Fixes: fddddb52a6c4 ('bus: introduce an Marvell EBU MBus driver')
Cc: <stable@vger.kernel.org> # v3.10+
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Link: https://lkml.kernel.org/r/1397823593-1932-7-git-send-email-thomas.petazzoni@free-electrons.com
Tested-by: Neil Greatorex <neil@fatboyfat.co.uk>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>