net: atm: Fix warnings in net/atm/lec.c when !CONFIG_PROC_FS

This patch fixes the following warnings when CONFIG_PROC_FS is not set:

linux/net/atm/lec.c: In function ‘lane_module_cleanup’:
linux/net/atm/lec.c:1062:27: error: ‘atm_proc_root’ undeclared (first
use in this function)
remove_proc_entry("lec", atm_proc_root);
                           ^
linux/net/atm/lec.c:1062:27: note: each undeclared identifier is
reported only once for each function it appears in

Signed-off-by: Augusto Mecking Caringi <augustocaringi@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>