s390/ccwgroup: Fix memory corruption

commit 0b60f9ea (s390: use
device_remove_file_self() instead of device_schedule_callback())

caused random memory corruption on my s390 box. Turns out that the
last element of the ccwgroup structure is of dynamic size, so we
must move the newly introduced work structure _before_ the zero
length array.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
CC: Tejun Heo <tj@kernel.org>
CC: Martin Schwidefsky <schwidefsky@de.ibm.com>
CC: Heiko Carstens <heiko.carstens@de.ibm.com>
CC: Sebastian Ott <sebott@linux.vnet.ibm.com>
CC: Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>