Merge branch 'bpf-fix-warning-in-bpf_trampoline_multi_detach'

Leon Hwang says:

====================
bpf: Fix WARNING in bpf_trampoline_multi_detach

Since tracing_multi link does not set ftrace_managed, it would fail to
release the tracing_multi link when attaching tracing_multi link and
then attaching fentry link.

[    3.714215] WARNING: kernel/bpf/trampoline.c:1727 at bpf_trampoline_multi_detach+0x20b/0x240, CPU#1: test_progs/97
...
[    3.733170]  bpf_tracing_multi_link_release+0x14/0x30
[    3.733890]  bpf_link_free+0x58/0x130
[    3.734414]  bpf_link_release+0x23/0x30

Fix it by setting 'ftrace_managed = true' in register_fentry_multi().

Note: the reason of targeting bpf-next tree is I'm planning to add
tracing_multi link support for bpf progs, that would rely on the fix and
have code conflict with the test.

Changes:
v1 -> v2:
* Collect Acked-by from Jiri, thanks.
* Check arg using tracing_multi_arg_check() in bpf prog in test.
  (per Sashiko)
* v1: https://lore.kernel.org/bpf/20260710144734.78203-1-leon.hwang@linux.dev/
====================

Link: https://patch.msgid.link/20260711124822.29406-1-leon.hwang@linux.dev
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>