bpf: cgroup_iter: support cgroup1 using cgroup fd

Use cgroup_v1v2_get_from_fd() in cgroup_iter to support attaching to
both cgroup v1 and v2 using fds.

Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Acked-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Tejun Heo <tj@kernel.org>

Author: yosrym93

kernel/bpf/cgroup_iter.c

@@ -196,7 +196,7 @@ static int bpf_iter_attach_cgroup(struct bpf_prog *prog,
 		return -EINVAL;
 
 	if (fd)
-		cgrp = cgroup_get_from_fd(fd);
+		cgrp = cgroup_v1v2_get_from_fd(fd);
 	else if (id)
 		cgrp = cgroup_get_from_id(id);
 	else /* walk the entire hierarchy by default. */