bpf: Fix comment for helper bpf_current_task_under_cgroup()

stable inclusion
from stable-v5.10.110
commit 73f2f37417b035d9607888be4fd23a9e709a85c6
bugzilla: https://gitee.com/openeuler/kernel/issues/I574AL

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=73f2f37417b035d9607888be4fd23a9e709a85c6



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commit 58617014 upstream.

Fix the descriptions of the return values of helper bpf_current_task_under_cgroup().

Fixes: c6b5fb86 ("bpf: add documentation for eBPF helpers (42-50)")
Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20220310155335.1278783-1-hengqi.chen@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Yu Liao <liaoyu15@huawei.com>
Reviewed-by: Wei Li <liwei391@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>