[PATCH] kill open-coded offsetof in cm4000_cs.c ZERO_DEV()

... to make sure that it doesn't break again when a field changes (see
"[PATCH] pcmcia: fix zeroing of cm4000_cs.c data" for recent example).

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>