[ATM]: Fix dereference of uninitialized pointer in zatm

Fixing breakage from [NET]: Kill skb->list - original was
	assign vcc
	do a bunch of stuff using ZATM_VCC(vcc)->pool as common subexpression
Now we do
	int pos = ZATM_VCC(vcc)->pool;
	assign vcc
	do a bunch of stuff
even though vcc is not even initialized when we enter that block...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>