edtlib: amend Node.props API documentation

Node properties are not created for all properties defined
by the node's binding (Binding.prop2specs),
only for those that actually have a value.

Signed-off-by: Christophe Dufaza <chris@openmarl.org>

scripts/dts/python-devicetree/src/devicetree/edtlib.py

@@ -962,8 +962,9 @@ class Node:
 
     props:
       A dict that maps property names to Property objects.
-      Property objects are created for all devicetree properties on the node
+      Property objects are created for the devicetree properties
-      that are mentioned in 'properties:' in the binding.
+      defined by the node's binding and that have a default value
+      or for which a value is set in the DTS.
 
     aliases:
       A list of aliases for the node. This is fetched from the /aliases node.