net: hdlc_x25: Remove unnecessary skb_reset_network_header calls

1. In x25_xmit, skb_reset_network_header is not necessary before we call
lapb_data_request. The lapb module doesn't need skb->network_header.
So there is no need to set skb->network_header before calling
lapb_data_request.

2. In x25_data_indication (called by the lapb module after data have
been received), skb_reset_network_header is not necessary before we
call netif_rx. After we call netif_rx, the code in net/core/dev.c will
call skb_reset_network_header before handing the skb to upper layers
(in __netif_receive_skb_core, called by __netif_receive_skb_one_core,
called by __netif_receive_skb, called by process_backlog). So we don't
need to call skb_reset_network_header by ourselves.

Cc: Martin Schiller <ms@dev.tdt.de>
Signed-off-by: Xie He <xie.he.0141@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>