x86, nmi_watchdog: Remove all stub function calls from old nmi_watchdog

Now that the bulk of the old nmi_watchdog is gone, remove all
the stub variables and hooks associated with it.

This touches lots of files mainly because of how the io_apic
nmi_watchdog was implemented.  Now that the io_apic nmi_watchdog
is forever gone, remove all its fingers.

Most of this code was not being exercised by virtue of
nmi_watchdog != NMI_IO_APIC, so there shouldn't be anything to
risky here.

Signed-off-by: Don Zickus <dzickus@redhat.com>
Cc: fweisbec@gmail.com
Cc: gorcunov@openvz.org
LKML-Reference: <1289578944-28564-3-git-send-email-dzickus@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>