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/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 847ab41..5284cd2 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -555,10 +555,8 @@
 void __init init_c1e_mask(void)
 {
 	/* If we're using c1e_idle, we need to allocate c1e_mask. */
-	if (pm_idle == c1e_idle) {
-		alloc_cpumask_var(&c1e_mask, GFP_KERNEL);
-		cpumask_clear(c1e_mask);
-	}
+	if (pm_idle == c1e_idle)
+		zalloc_cpumask_var(&c1e_mask, GFP_KERNEL);
 }
 
 static int __init idle_setup(char *str)