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/acpi/processor_throttling.c b/drivers/acpi/processor_throttling.c
index ce7cf3b..4c6c14c 100644
--- a/drivers/acpi/processor_throttling.c
+++ b/drivers/acpi/processor_throttling.c
@@ -77,7 +77,7 @@
 	struct acpi_tsd_package *pdomain, *match_pdomain;
 	struct acpi_processor_throttling *pthrottling, *match_pthrottling;
 
-	if (!alloc_cpumask_var(&covered_cpus, GFP_KERNEL))
+	if (!zalloc_cpumask_var(&covered_cpus, GFP_KERNEL))
 		return -ENOMEM;
 
 	/*
@@ -105,7 +105,6 @@
 	if (retval)
 		goto err_ret;
 
-	cpumask_clear(covered_cpus);
 	for_each_possible_cpu(i) {
 		pr = per_cpu(processors, i);
 		if (!pr)