Fix clang -Wvarargs compile errors

error: passing an object that undergoes default argument promotion to
'va_start' has undefined behavior [-Werror,-Wvarargs]

Change-Id: Id342beea916ec73e29e399087532caecfa19055f
Signed-off-by: Damjan Marion <damarion@cisco.com>
diff --git a/src/vnet/fib/fib_test.h b/src/vnet/fib/fib_test.h
index 53697cb..0309b3f 100644
--- a/src/vnet/fib/fib_test.h
+++ b/src/vnet/fib/fib_test.h
@@ -118,11 +118,11 @@
                                    va_list *ap);
 
 extern int fib_test_validate_lb_v(const load_balance_t *lb,
-                                  u16 n_buckets,
+                                  int n_buckets,
                                   va_list *ap);
 
 extern int fib_test_validate_lb(const dpo_id_t *dpo,
-				u16 n_buckets,
+				int n_buckets,
 				...);
 
 extern int fib_test_validate_entry(fib_node_index_t fei,