Add maintainer for GTPU Plugin

Change-Id: Ic8cecdee7ae74a6b816e0a02985c456fd3ec8d8f
Signed-off-by: Hongjun Ni <hongjun.ni@intel.com>
diff --git a/MAINTAINERS b/MAINTAINERS
index 0f5dfc0..edd873e 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -122,6 +122,11 @@
 F:	src/plugins/sixrd/
 F:	src/plugins/sixrd.am
 
+Plugin - GTPU
+M:      Hongjun Ni <hongjun.ni@intel.com>
+F:      src/plugins/gtpu/
+F:      src/plugins/gtpu.am
+
 Test Infrastructure
 M:	Klement Sekera <ksekera@cisco.com>
 F:	test/