mem: Merge ranges in bus before passing them on

mem: Merge ranges in bus before passing them on

This patch adds basic merging of address ranges to the bus, such that
interleaved ranges are merged together before being passed on by the
bus. As such, the bus aggregates the address ranges of the connected
slave ports and then passes on the merged ranges through its master
ports. The bus thus hides the complexity of the interleaved ranges and
only exposes contigous ranges to the surrounding system.

As part of this patch, the bus ranges are also cached for any future
queries.