Add support for multiple floors, ie. cascaded docg3
chips. There might be 4 docg3 chips cascaded, sharing the
same address space, and providing up to 4 times the storage
capacity of a unique chip.
Each floor will be seen as an independant mtd device.
Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr> Reviewed-by: Ivan Djelic <ivan.djelic@parrot.com> Reviewed-by: Mike Dunn <mikedunn@newsguy.com> Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>