[PATCH] dscc4 compile fix for hdlc

[PATCH] dscc4 compile fix for hdlc

From: Francois Romieu <romieu@fr.zoreil.com>

The wan driver I maintain was hit by hdlc changes too. Please
apply patch below. It is diffed against plain -test2 but it
applies equally as well against -test2-mm2.

More important changes will come in a near future for this
driver but I'd rather keep the changes separated.

Description:
- after the hdlc changes, dscc4 module doesn't need to set
  hdlc->proto(.id) itself anymore;
- MOD_{INC/DEC}_USE_COUNT removal;
- SET_NETDEV_DEV() use;