percpu: zero memory more efficiently in mm/percpu.c::pcpu_mem_alloc()

Don't do vmalloc() + memset() when vzalloc() will do.

tj: dropped unnecessary temp variable ptr.
Signed-off-by: NJesper Juhl <jj@chaosbits.net>
Signed-off-by: NTejun Heo <tj@kernel.org>

mm/percpu.c

@@ -293,12 +293,8 @@ static void *pcpu_mem_alloc(size_t size)
 
 	if (size <= PAGE_SIZE)
 		return kzalloc(size, GFP_KERNEL);
-	else {
-		void *ptr = vmalloc(size);
-		if (ptr)
-			memset(ptr, 0, size);
-		return ptr;
-	}
+	else
+		return vzalloc(size);
 }
 
 /**