Changes:
   o Added permission checks for installing. CAP_SYS_ADMIN and
     CAP_SYS_TTY_CONFIG can install the ldisc.
   o Check if allocation of skb was successful.
Signed-off-by: NSjur Braendeland <sjur.brandeland@stericsson.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>