namespaces Kconfig: remove the cgroup device whitelist experimental tag

This subsystem is merged since a long time now, I think we can consider it
mature enough.

Signed-off-by: Daniel Lezcano <daniel.lezcano@free.fr>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: "Serge E. Hallyn" <serue@us.ibm.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Paul Menage <menage@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

init/Kconfig

@@ -542,7 +542,6 @@ config CGROUP_FREEZER
 
 config CGROUP_DEVICE
 	bool "Device controller for cgroups"
-	depends on EXPERIMENTAL
 	help
 	  Provides a cgroup implementing whitelists for devices which
 	  a process in the cgroup can mknod or open.