core: support cgroup v2 device controller

Cgroup v2 provides the eBPF-based device controller, which isn't currently
supported by systemd. This commit aims to provide such support.

There are no user-visible changes, just the device policy and whitelist
start working if cgroup v2 is used.

src/basic/cgroup-util.c

@@ -2768,6 +2768,7 @@ static const char *cgroup_controller_table[_CGROUP_CONTROLLER_MAX] = {
         [CGROUP_CONTROLLER_DEVICES] = "devices",
         [CGROUP_CONTROLLER_PIDS] = "pids",
         [CGROUP_CONTROLLER_BPF_FIREWALL] = "bpf-firewall",
+        [CGROUP_CONTROLLER_BPF_DEVICES] = "bpf-devices",
 };
 
 DEFINE_STRING_TABLE_LOOKUP(cgroup_controller, CGroupController);