MLBEDSW-8886: Regression: Output diff on LSTM

 - Fix regression caused by too strict constraints on
SplitSpliceRead causing output diff for LSTM.
 - As long as the SplitSpliceRead shape fits within the
consumer ifm shape it is ok to move the read.

Change-Id: Ia6f508f99638c3aedccc7fd9f31405527bb64f87
Signed-off-by: Johan Alfven <johan.alfven@arm.com>