sync to latest libbpf repo

Sync to latest libbpf repo. New helper bpf_jiffies64
and new program type BPF_PROG_TYPE_EXT is added.

Signed-off-by: Yonghong Song <yhs@fb.com>
diff --git a/introspection/bps.c b/introspection/bps.c
index 4190fb8..c5984c4 100644
--- a/introspection/bps.c
+++ b/introspection/bps.c
@@ -44,6 +44,7 @@
   [BPF_PROG_TYPE_CGROUP_SOCKOPT] = "cgroup_sockopt",
   [BPF_PROG_TYPE_TRACING] = "tracing",
   [BPF_PROG_TYPE_STRUCT_OPS] = "struct_ops",
+  [BPF_PROG_TYPE_EXT] = "ext",
 };
 
 static const char * const map_type_strings[] = {