sync: latest libbpf changes from kernel

Syncing latest libbpf commits from kernel repository.
Baseline bpf-next commit:   ca4db6389d611eee2eb7c1dfe710b62d8ea06772
Checkpoint bpf-next commit: 6b207d66aa9fad0deed13d5f824e1ea193b0a777
Baseline bpf commit:        2bdeb3ed547d8822b2566797afa6c2584abdb119
Checkpoint bpf commit:      e708e2bd55c921f5bb554fa5837d132a878951cf

Andrii Nakryiko (1):
  libbpf: Make bpf_endian co-exist with vmlinux.h

Song Liu (1):
  bpf: Introduce helper bpf_get_task_stack()

 include/uapi/linux/bpf.h | 37 +++++++++++++++++++++++++++++++++-
 src/bpf_endian.h         | 43 ++++++++++++++++++++++++++++++++--------
 2 files changed, 71 insertions(+), 9 deletions(-)

--
2.24.1

BPF-CHECKPOINT-COMMIT

@@ -1 +1 @@
-2bdeb3ed547d8822b2566797afa6c2584abdb119
+e708e2bd55c921f5bb554fa5837d132a878951cf

CHECKPOINT-COMMIT

@@ -1 +1 @@
-ca4db6389d611eee2eb7c1dfe710b62d8ea06772
+6b207d66aa9fad0deed13d5f824e1ea193b0a777