s390/watchdog: support for KVM hypervisors and delete pr_info messages

This patch extends the diag288 watchdog driver to be able to deal with KVM
hypervisors. Only z/VM needs special handling, we can use the same interface
as on LPAR. Remove all pr_info output to avoid misconception. Because there
is no value in these messages and only the pr_err messages make sense.

Signed-off-by: Xu Wang <gesaint@linux.vnet.ibm.com>
Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>