watchdog: implement error handling for failure to set up hardware perf events

If watchdog_nmi_enable() fails to set up the hardware perf event of one
CPU, the entire hard lockup detector is deemed unreliable.  Hence, disable
the hard lockup detector and shut down the hardware perf events on all
CPUs.

[dzickus@redhat.com: update comments to explain some code]
Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com>
Signed-off-by: Don Zickus <dzickus@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>