drivers/net/wireless/ath/ath9k: Use kmemdup

Use kmemdup when some other buffer is immediately copied into the
allocated region.

A simplified version of the semantic patch that makes this change is as
follows: (http://coccinelle.lip6.fr/)

// <smpl>
@@
expression from,to,size,flag;
statement S;
@@

-  to = \(kmalloc\|kzalloc\)(size,flag);
+  to = kmemdup(from,size,flag);
   if (to==NULL || ...) S
-  memcpy(to, from, size);
// </smpl>

Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath9k/hif_usb.c

@@ -907,12 +907,10 @@ static void ath9k_hif_usb_reboot(struct usb_device *udev)
 	void *buf;
 	int ret;
 
-	buf = kmalloc(4, GFP_KERNEL);
+	buf = kmemdup(&reboot_cmd, 4, GFP_KERNEL);
 	if (!buf)
 		return;
 
-	memcpy(buf, &reboot_cmd, 4);
-
 	ret = usb_bulk_msg(udev, usb_sndbulkpipe(udev, USB_REG_OUT_PIPE),
 			   buf, 4, NULL, HZ);
 	if (ret)