Tweak cockpit main needle to work on ppc64 too

We don't get a CPU model on ppc64, we get a machine ID everywhere
(I hope).

Signed-off-by: Adam Williamson <awilliam@redhat.com>

needles/cockpit/cockpit_main-cockpit209-20191214.json

@@ -1,15 +1,15 @@
-{
-  "area": [
-    {
-      "ypos": 696,
-      "type": "match",
-      "height": 15,
-      "width": 43,
-      "xpos": 378
-    }
-  ],
-  "properties": [],
-  "tags": [
-    "cockpit_main"
-  ]
+{
+    "area": [
+        {
+            "height": 15,
+            "type": "match",
+            "width": 73,
+            "xpos": 378,
+            "ypos": 731
+        }
+    ],
+    "properties": [],
+    "tags": [
+        "cockpit_main"
+    ]
 }