This patch adds a selftest suite to validate the cgroup kfuncs that were
added in the prior patch.
Signed-off-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/20221122055458.173143-3-void@manifault.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>