[PATCH] allow drivers to claim the lapic NMI watchdog HW

[PATCH] allow drivers to claim the lapic NMI watchdog HW

Here is an updated lapic NMI ownership tracking patch which
should address the issues that were raised with the first one:

- Simplified the API function names to {reserve,release}_lapic_nmi().

- Rewrote the ownership tracking code to use two individually named
  flags instead of using arithmetic and the sign. The code is now
  simple enough that no "hiding" macros are needed. (Thanks Albert
  for that suggestion.)