[ATM]: Use seq_open/release_privade instead of manual manipulations.

lec_seq_open/lec_seq_release and __vcc_seq_open/vcc_seq_release
do seq_open/release_private's job.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>