selinux: don't bother with selinuxfs_info_free() on failures

Failures in sel_fill_super() will be followed by sel_kill_sb(), which
will call selinuxfs_info_free() anyway.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Reviewed-by: Christian Brauner <brauner@kernel.org>
[PM: subj and description tweaks]
Signed-off-by: Paul Moore <paul@paul-moore.com>