bpf: cgroup: fix documentation of __cgroup_bpf_update()

There's a 'not' missing in one paragraph. Add it.

Fixes: 3007098 ("cgroup: add support for eBPF programs")
Signed-off-by: Daniel Mack <daniel@zonque.org>
Reported-by: Rami Rosen <roszenrami@gmail.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

kernel/bpf/cgroup.c

@@ -66,8 +66,8 @@ void cgroup_bpf_inherit(struct cgroup *cgrp, struct cgroup *parent)
  * Each cgroup has a set of two pointers for bpf programs; one for eBPF
  * programs it owns, and which is effective for execution.
  *
- * If @prog is %NULL, this function attaches a new program to the cgroup and
- * releases the one that is currently attached, if any. @prog is then made
+ * If @prog is not %NULL, this function attaches a new program to the cgroup
+ * and releases the one that is currently attached, if any. @prog is then made
  * the effective program of type @type in that cgroup.
  *
  * If @prog is %NULL, the currently attached program of type @type is released,