syncppp: Fix crashes.

The syncppp layer wants a mid-level netdev private pointer.

It was using netdev->priv but that only worked by accident,
and thus this scheme was broken when the device private
allocation strategy changed.

Add a proper mid-layer private pointer for uses like this,
update syncppp and all users, and remove the HDLC_PPP broken
tag from drivers/net/wan/Kconfig

Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/wan/lmc/lmc_main.c

@@ -891,6 +891,7 @@ static int __devinit lmc_init_one(struct pci_dev *pdev,
 
     /* Initialize the sppp layer */
     /* An ioctl can cause a subsequent detach for raw frame interface */
+    dev->ml_priv = sc;
     sc->if_type = LMC_PPP;
     sc->check = 0xBEAFCAFE;
     dev->base_addr = pci_resource_start(pdev, 0);