s390/vmwatchdog: do not use static data

s390/vmwatchdog: do not use static data

Using static data for fields which are accessed by HW will fail if
the driver is build as a module (since this would be vmalloc'ed
memory). This Bug was revealed via
"s390: remove virt_to_phys implementation" - the old virt_to_phys
implementation would have translated the address but it was not
guaranteed that the memory was contiguous.

Fix it by putting the data on the stack.

Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>