wan: dscc4: fix build warning Wunused-but-set-variable

Fix:
drivers/net/wan/dscc4.c: In function 'dscc4_open':
drivers/net/wan/dscc4.c:1049:25: warning: variable 'ppriv' set but not used
[-Wunused-but-set-variable]

This has been in there unused since 1da177e4

 (Linux-2.6.12-rc2) simply
remove it.

Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>