cpumask: fix compile error when CONFIG_NR_CPUS is not defined

CONFIG_NR_CPUS will be defined for all arch's whether SMP or not, but
it may not have made it into all arches yet.

Signed-off-by: Mike Travis <[e-mail]>
Signed-off-by: Ingo Molnar <[e-mail]>

drivers/base/cpu.c

···
  */
 static ssize_t print_cpus_kernel_max(struct sysdev_class *class, char *buf)
 {
-	int n = snprintf(buf, PAGE_SIZE-2, "%d\n", CONFIG_NR_CPUS - 1);
+	int n = snprintf(buf, PAGE_SIZE-2, "%d\n", NR_CPUS - 1);
 	return n;
 }
 static SYSDEV_CLASS_ATTR(kernel_max, 0444, print_cpus_kernel_max, NULL);