fix(morello): dts: add model names

The core root node DT bindings require every DT to have a "model"
property. Linux' "make dtbs_check" reports:
============
.../morello-soc.dt.yaml: /: 'model' is a required property
     From schema: dt-schema.git/dtschema/schemas/root-node.yaml
============

Add a model name to both the SoC and FVP files to improve bindings
compliance.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Change-Id: I64923edb947f8939dfa24c13a37996b1ba34ea54
2 files changed