Explicitly mark unused parameters to resolve warnings

Reduce log spam during build.

Change-Id: Id0734c3a5bc08f728ca868a5a18375d8fc16bae6
diff --git a/json_object.c b/json_object.c
index 8ed0239..08af06f 100644
--- a/json_object.c
+++ b/json_object.c
@@ -456,8 +456,8 @@
 
 static int json_object_boolean_to_json_string(struct json_object* jso,
 					      struct printbuf *pb,
-					      int level,
-						  int flags)
+					      int UNUSED(level),
+						  int UNUSED(flags))
 {
 	if (jso->o.c_boolean)
 		return sprintbuf(pb, "true");
@@ -499,8 +499,8 @@
 
 static int json_object_int_to_json_string(struct json_object* jso,
 					  struct printbuf *pb,
-					  int level,
-					  int flags)
+					  int UNUSED(level),
+					  int UNUSED(flags))
 {
 	return sprintbuf(pb, "%"PRId64, jso->o.c_int64);
 }
@@ -591,7 +591,7 @@
 
 static int json_object_double_to_json_string(struct json_object* jso,
 					     struct printbuf *pb,
-					     int level,
+					     int UNUSED(level),
 						 int flags)
 {
   char buf[128], *p, *q;
@@ -659,14 +659,14 @@
 }
 
 int json_object_userdata_to_json_string(struct json_object *jso,
-	struct printbuf *pb, int level, int flags)
+	struct printbuf *pb, int UNUSED(level), int UNUSED(flags))
 {
 	int userdata_len = strlen(jso->_userdata);
 	printbuf_memappend(pb, jso->_userdata, userdata_len);
 	return userdata_len;
 }
 
-void json_object_free_userdata(struct json_object *jso, void *userdata)
+void json_object_free_userdata(struct json_object *UNUSED(jso), void *userdata)
 {
 	free(userdata);
 }
@@ -725,8 +725,8 @@
 
 static int json_object_string_to_json_string(struct json_object* jso,
 					     struct printbuf *pb,
-					     int level,
-						 int flags)
+					     int UNUSED(level),
+						 int UNUSED(flags))
 {
 	sprintbuf(pb, "\"");
 	json_escape_str(pb, jso->o.c_string.str, jso->o.c_string.len);