tools/bpftool: Add ringbuf map to a list of known map types

Add symbolic name "ringbuf" to map to BPF_MAP_TYPE_RINGBUF. Without this,
users will see "type 27" instead of "ringbuf" in `map show` output.
Signed-off-by: NAndrii Nakryiko <andriin@fb.com>
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200615225355.366256-1-andriin@fb.com

tools/bpf/bpftool/map.c

@@ -49,6 +49,7 @@ const char * const map_type_name[] = {
 	[BPF_MAP_TYPE_STACK]			= "stack",
 	[BPF_MAP_TYPE_SK_STORAGE]		= "sk_storage",
 	[BPF_MAP_TYPE_STRUCT_OPS]		= "struct_ops",
+	[BPF_MAP_TYPE_RINGBUF]			= "ringbuf",
 };
 
 const size_t map_type_name_size = ARRAY_SIZE(map_type_name);