cpumask: use zalloc_cpumask_var() where possible

Remove open-coded zalloc_cpumask_var() and zalloc_cpumask_var_node().

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/drivers/oprofile/buffer_sync.c b/drivers/oprofile/buffer_sync.c
index 8574622..c9e2ae9 100644
--- a/drivers/oprofile/buffer_sync.c
+++ b/drivers/oprofile/buffer_sync.c
@@ -154,9 +154,8 @@
 {
 	int err;
 
-	if (!alloc_cpumask_var(&marked_cpus, GFP_KERNEL))
+	if (!zalloc_cpumask_var(&marked_cpus, GFP_KERNEL))
 		return -ENOMEM;
-	cpumask_clear(marked_cpus);
 
 	start_cpu_work();