ddr: marvell: a38x: import header change from upstream

commit 3908e20c6c520339e9bddb566823ae5e065d5218 upstream.

The commit mentioned above changes non-DDR3 stuff in upstream, but it
also changes header ddr_topology_def.h.

Import this header change to remain consistent with upstream.

Signed-off-by: Marek Behún <marek.behun@nic.cz>
Tested-by: Chris Packham <chris.packham@alliedtelesis.co.nz>