[PATCH] isdn/gigaset: avoid cs->dev null pointer dereference

When gigaset_initbcs() is called, cs->dev is not initialized yet.  If
dev_alloc_skb() failed in this function, NULL poinster dereference will
happen at dev_warn().

Cc: Kai Germaschewski <kai.germaschewski@gmx.de>
Cc: Hansjoerg Lipp <hjlipp@web.de>
Cc: Tilman Schmidt <tilman@imap.cc>
Acked-by: Karsten Keil <kkeil@suse.de>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>