COMPMID-415: Move SoftmaxLayer to new validation

Change-Id: I68bb359021256e67892e4fc00d436f9027a3bd07
Reviewed-on: http://mpd-gerrit.cambridge.arm.com/80942
Reviewed-by: Anthony Barbier <anthony.barbier@arm.com>
Tested-by: Kaizen <jeremy.johnson+kaizengerrit@arm.com>
14 files changed