schemas: root-node: Add 'television' chassis-type

The 'television' chassis-type includes Smart TVs and set-top boxes, or any
remote-controlled displays in general.

Signed-off-by: Nick Chan <towinchenmi@gmail.com>

dtschema/schemas/root-node.yaml

@@ -27,6 +27,7 @@ properties:
       - handset
       - watch
       - embedded
+      - television
   "#address-cells":
     enum: [1, 2]
   "#size-cells":