[WATCHDOG] hpwdt: Fix kdump when using hpwdt

When the "hpwdt" module is loaded (even if the /dev/watchdog device is not
opened), then kdump does not work. The panic kernel either does not start at
all or crash in various places.

The problem is that hpwdt_pretimeout is registered with register_die_notifier()
with the highest possible priority. Because it returns NOTIFY_STOP, the
crash_nmi_callback which is also registered with register_die_notifier()
is never executed. This causes the shutdown of other CPUs to fail.

Reverting the order is no option: The crash_nmi_callback executes HLT
and so never returns normally. Because of that, it must be executed as
last notifier, which currently is done.

So, that patch returns NOTIFY_OK to keep the crash_nmi_callback executed.

Signed-off-by: Bernhard Walle <bwalle@suse.de>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
Signed-off-by: Thomas Mingarelli <thomas.mingarelli@hp.com>
Cc: Vivek Goyal <vgoyal@redhat.com>