Disable hardware decoding by default on most platforms

Appears to cause heavy problems in some cases. Until this is fixed, I'd
rather require users to enable it manually, instead of having _all_
users run into potential issues.

resources/settings/settings_description.json

@@ -140,7 +140,15 @@
       },
       {
         "value": "hardware_decoding",
-        "default": true,
+        "default": [
+          {
+            "value": true,
+            "platforms": [ "oe" ]
+          },
+          {
+            "value": false
+          }
+        ],
         "platforms_excluded": "oe_rpi"
       },
       {