sync with latest libbpf repo

sync with latest libbpf repo

Signed-off-by: Yonghong Song <yhs@fb.com>
diff --git a/introspection/bps.c b/introspection/bps.c
index 7330d81..9d7659e 100644
--- a/introspection/bps.c
+++ b/introspection/bps.c
@@ -46,6 +46,7 @@
   [BPF_PROG_TYPE_STRUCT_OPS] = "struct_ops",
   [BPF_PROG_TYPE_EXT] = "ext",
   [BPF_PROG_TYPE_LSM] = "lsm",
+  [BPF_PROG_TYPE_SK_LOOKUP] = "sk_lookup",
 };
 
 static const char * const map_type_strings[] = {