Change back productID to be a number

Fixes serialport#1278 The productID should be a number not a description string

lib/bindings/linux-list.js

@@ -14,7 +14,7 @@ function propName(name) {
     'ID_VENDOR_ENC': 'manufacturer',
     'ID_SERIAL_SHORT': 'serialNumber',
     'ID_VENDOR_ID': 'vendorId',
-    'ID_MODEL_ENC': 'productId',
+    'ID_MODEL_ID': 'productId',
     'DEVLINKS': 'pnpId'
   }[name.toUpperCase()];
 }