arch/ia64: replace cpumask_weight with cpumask_empty where appropriate

setup_arch() calls cpumask_weight() to check if any bit of a given cpumask
is set. We can do it more efficiently with cpumask_empty() because
cpumask_empty() stops traversing the cpumask as soon as it finds first set
bit, while cpumask_weight() counts all bits unconditionally.
Signed-off-by: NYury Norov <yury.norov@gmail.com>

arch/ia64/kernel/setup.c

@@ -572,7 +572,7 @@ setup_arch (char **cmdline_p)
 #ifdef CONFIG_ACPI_HOTPLUG_CPU
 	prefill_possible_map();
 #endif
-	per_cpu_scan_finalize((cpumask_weight(&early_cpu_possible_map) == 0 ?
+	per_cpu_scan_finalize((cpumask_empty(&early_cpu_possible_map) ?
 		32 : cpumask_weight(&early_cpu_possible_map)),
 		additional_cpus > 0 ? additional_cpus : 0);
 #endif /* CONFIG_ACPI_NUMA */