tests/vty: fix use of GNU 'missing =' extension in designator

Change-Id: I66edb247898594b51cc9d7c1b3d0c60ba66fc637
diff --git a/tests/vty/vty_test.c b/tests/vty/vty_test.c
index 1db0d5c..e068f19 100644
--- a/tests/vty/vty_test.c
+++ b/tests/vty/vty_test.c
@@ -542,9 +542,9 @@
 			/* Reserved for libraries */
 			[VTY_TEST_ATTR_UPPER]	= 'X',
 			/* Reserved for global attribues */
-			[VTY_TEST_ATTR_RAFC_DOT]	'.',
-			[VTY_TEST_ATTR_RAFC_EXCL]	'!',
-			[VTY_TEST_ATTR_RAFC_AT]		'@',
+			[VTY_TEST_ATTR_RAFC_DOT]	= '.',
+			[VTY_TEST_ATTR_RAFC_EXCL]	= '!',
+			[VTY_TEST_ATTR_RAFC_AT]		= '@',
 		},
 	};