atm: iphase: fix misleading indention

Fix a smatch warning:
drivers/atm/iphase.c:1178 rx_pkt() warn: curly braces intended?

The code is correct, the indention is misleading. In case the allocation
of skb fails, we want to skip to the end.

Signed-off-by: Tillmann Heidsieck <theidsieck@leenox.de>
Signed-off-by: David S. Miller <davem@davemloft.net>