tlv: capitalize nonNegativeInteger -> NonNegativeInteger

Change-Id: I82c578142f801d3307eec49ee82b05dbdd5071aa
diff --git a/data.rst b/data.rst
index ee5995e..b225131 100644
--- a/data.rst
+++ b/data.rst
@@ -40,7 +40,7 @@
 
 ::
 
-    ContentType = CONTENT-TYPE-TYPE TLV-LENGTH nonNegativeInteger
+    ContentType = CONTENT-TYPE-TYPE TLV-LENGTH NonNegativeInteger
 
 The following ContentTypes are currently defined:
 
@@ -66,7 +66,7 @@
 
 ::
 
-    FreshnessPeriod = FRESHNESS-PERIOD-TYPE TLV-LENGTH nonNegativeInteger
+    FreshnessPeriod = FRESHNESS-PERIOD-TYPE TLV-LENGTH NonNegativeInteger
 
 The optional ``FreshnessPeriod`` indicates how long a node should wait after the arrival of this data before marking it "non-fresh".
 The encoded value is number of milliseconds.