bus: mvebu-mbus: Factorize Armada 370/XP data structures

These structures were only different in the mapping tables.
Now that those tables have been removed, it doesn't make any sense
to keep different structures.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Tested-by: Andrew Lunn <andrew@lunn.ch>
Tested-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>