[ATM] net/atm/clip.c: fix PROC_FS=n compile

This patch fixes the following compile error with CONFIG_PROC_FS=n by 
reverting commit dcdb0275:

<--  snip  -->

...
  CC      net/atm/clip.o
net/atm/clip.c: In function ‘atm_clip_init’:
net/atm/clip.c:975: error: ‘atm_proc_root’ undeclared (first use in this function)
net/atm/clip.c:975: error: (Each undeclared identifier is reported only once
net/atm/clip.c:975: error: for each function it appears in.)
net/atm/clip.c:977: error: ‘arp_seq_fops’ undeclared (first use in this function)
make[2]: *** [net/atm/clip.o] Error 1

<--  snip  -->

Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: David S. Miller <davem@davemloft.net>