MLBEDSW-2556: Odd core/block depth weight interleaving update

 - If blockdepth or core count resulted in empty or non-existent substreams, the
   command generator generated an error. This commit changes the command stream
   generator to only program cores that have streams and are enabled for the
   configuration.

Change-Id: I4e724b19de14d3a12e886ec6b17d0038593dfb59
Signed-off-by: Tim Hall <tim.hall@arm.com>