selinux: ioctl_has_perm should be static

Fixes the following sparse warning:

 security/selinux/hooks.c:3242:5: warning: symbol 'ioctl_has_perm' was
 not declared. Should it be static?

Signed-off-by: Geliang Tang <geliangtang@163.com>
Acked-by: Jeff Vander Stoep <jeffv@google.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <pmoore@redhat.com>