BpfMap: Specify zero to be default map_flags in constructor

Bug: 149963652
Test: atest
Change-Id: I0a9311bdadffc0fda75f153b3e2617fb082d3ddb
diff --git a/libbpf_android/include/bpf/BpfMap.h b/libbpf_android/include/bpf/BpfMap.h
index 9fdcebb..8c35931 100644
--- a/libbpf_android/include/bpf/BpfMap.h
+++ b/libbpf_android/include/bpf/BpfMap.h
@@ -57,7 +57,7 @@
   public:
     explicit BpfMap<Key, Value>(const char* pathname) : BpfMap<Key, Value>(pathname, 0) {}
 
-    BpfMap<Key, Value>(bpf_map_type map_type, uint32_t max_entries, uint32_t map_flags) {
+    BpfMap<Key, Value>(bpf_map_type map_type, uint32_t max_entries, uint32_t map_flags = 0) {
         int map_fd = createMap(map_type, sizeof(Key), sizeof(Value), max_entries, map_flags);
         if (map_fd >= 0) mMapFd.reset(map_fd);
     }