Add missing skb->dev assignment in Frame Relay RX code

Commit 4c13eb66 ([ETH]: Make
eth_type_trans set skb->dev like the other *_type_trans) removed
skb->dev assignment from hdlc_fr.c:fr_rx(). Unfortunately it was also
needed for cases other than eth_type_trans().

Adding it back.

It's quite serious and may be a security risk as it causes a wrong
input interface indication (the physical hdlcX instead of logical
pvcX). Probably -stable class fix.

Signed-off-by: Krzysztof Halasa <khc@pm.waw.pl>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>