[PATCH] i386: Clean up NMI watchdog code

- Introduce a wd_ops structure
- Convert the various nmi watchdogs over to it
- This allows to split the perfctr reservation from the watchdog
setup cleanly.
- Do perfctr reservation globally as it should have always been
- Remove dead code referenced only by unused EXPORT_SYMBOLs

Signed-off-by: Andi Kleen <ak@suse.de>