cpumask: make CONFIG_NR_CPUS always valid.

Impact: cleanup

Currently we have NR_CPUS, which is 1 on UP, and CONFIG_NR_CPUS on
SMP.  If we make CONFIG_NR_CPUS always valid (and always 1 on !SMP),
we can skip the middleman.

This also allows us to find and check all the unaudited NR_CPUS usage
as we prepare for v. large NR_CPUS.

To avoid breaking every arch, we cheat and do this for the moment
in the header if the arch doesn't.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Mike Travis <travis@sgi.com>

include/linux/threads.h

@@ -8,17 +8,17 @@
  */
 
 /*
- * Maximum supported processors that can run under SMP.  This value is
- * set via configure setting.  The maximum is equal to the size of the
- * bitmasks used on that platform, i.e. 32 or 64.  Setting this smaller
- * saves quite a bit of memory.
+ * Maximum supported processors.  Setting this smaller saves quite a
+ * bit of memory.  Use nr_cpu_ids instead of this except for static bitmaps.
  */
-#ifdef CONFIG_SMP
-#define NR_CPUS		CONFIG_NR_CPUS
-#else
-#define NR_CPUS		1
+#ifndef CONFIG_NR_CPUS
+/* FIXME: This should be fixed in the arch's Kconfig */
+#define CONFIG_NR_CPUS	1
 #endif
 
+/* Places which use this should consider cpumask_var_t. */
+#define NR_CPUS		CONFIG_NR_CPUS
+
 #define MIN_THREADS_LEFT_FOR_ROOT 4
 
 /*