security: filesystem capabilities no longer experimental

Filesystem capabilities have come of age.  Remove the experimental tag for
configuring filesystem capabilities.

Signed-off-by: Andrew G. Morgan <morgan@kernel.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>