scripts/dts: Fix bug in dead /memreserve/ code

The /memreserve/ code would crash if it ever ran, because 'name' isn't
defined (seems to be some copy-paste here). There are no /memreserve/s
in Zephyr though, so it works out.

'name' seems to be the node name. Not sure what to put for a
/memreserve/, but make it '<memreserve>' to make it stand out.

Fixes a pylint warning.

Signed-off-by: Ulf Magnusson <Ulf.Magnusson@nordicsemi.no>
diff --git a/scripts/dts/devicetree.py b/scripts/dts/devicetree.py
index 10e8e86..02d209d 100755
--- a/scripts/dts/devicetree.py
+++ b/scripts/dts/devicetree.py
@@ -212,7 +212,7 @@
                 'reg': [start, end],
                 'label': label,
                 'addr': start,
-                'name': build_node_name(name, start)
+                'name': '<memreserve>'
             }
         elif line.endswith('{'):
             if not has_v1_tag and not ignore_dts_version: