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>

security/selinux/hooks.c

@@ -3235,7 +3235,7 @@ static void selinux_file_free_security(struct file *file)
  * Check whether a task has the ioctl permission and cmd
  * operation to an inode.
  */
-int ioctl_has_perm(const struct cred *cred, struct file *file,
+static int ioctl_has_perm(const struct cred *cred, struct file *file,
 		u32 requested, u16 cmd)
 {
 	struct common_audit_data ad;