s390/watchdog: use watchdog API

Converted the vmwatchdog driver to use the kernel's watchdog API.

Signed-off-by: Philipp Hachtmann <phacht@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/configs/performance_defconfig b/arch/s390/configs/performance_defconfig
index b5ba8fe..54ebb85 100644
--- a/arch/s390/configs/performance_defconfig
+++ b/arch/s390/configs/performance_defconfig
@@ -451,6 +451,7 @@
 CONFIG_WATCHDOG=y
 CONFIG_WATCHDOG_NOWAYOUT=y
 CONFIG_SOFT_WATCHDOG=m
+CONFIG_DIAG288_WATCHDOG=m
 # CONFIG_HID is not set
 # CONFIG_USB_SUPPORT is not set
 CONFIG_INFINIBAND=m