SELinux: drop secondary_ops->sysctl

We are still calling secondary_ops->sysctl even though the capabilities
module does not define a sysctl operation.

Signed-off-by: Eric Paris <eparis@redhat.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>