x86: cleanup some remaining usages of NR_CPUS where s/b nr_cpu_ids

Impact: Reduce future system panics due to cpumask operations using NR_CPUS

Insure that code does not look at bits >= nr_cpu_ids as when cpumasks are
allocated based on nr_cpu_ids, these extra bits will not be defined.

Also some other minor updates:

   * change in to use cpu accessor function set_cpu_present() instead of
     directly accessing cpu_present_map w/cpu_clear() [arch/x86/kernel/reboot.c]

   * use cpumask_of() instead of &cpumask_of_cpu() [arch/x86/kernel/reboot.c]

   * optimize some cpu_mask_to_apicid_and functions.

Signed-off-by: Mike Travis <travis@sgi.com>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/include/asm/lguest.h b/arch/x86/include/asm/lguest.h
index d28a507..1caf576 100644
--- a/arch/x86/include/asm/lguest.h
+++ b/arch/x86/include/asm/lguest.h
@@ -15,7 +15,7 @@
 #define SHARED_SWITCHER_PAGES \
 	DIV_ROUND_UP(end_switcher_text - start_switcher_text, PAGE_SIZE)
 /* Pages for switcher itself, then two pages per cpu */
-#define TOTAL_SWITCHER_PAGES (SHARED_SWITCHER_PAGES + 2 * NR_CPUS)
+#define TOTAL_SWITCHER_PAGES (SHARED_SWITCHER_PAGES + 2 * nr_cpu_ids)
 
 /* We map at -4M for ease of mapping into the guest (one PTE page). */
 #define SWITCHER_ADDR 0xFFC00000