media: media/usb: Use kmemdup rather than duplicating its implementation

kmemdup is introduced to duplicate a region of memory in a neat way.
Rather than kmalloc/kzalloc + memcpy, which the programmer needs to
write the size twice (sometimes lead to mistakes), kmemdup improves
readability, leads to smaller code and also reduce the chances of mistakes.
Suggestion to use kmemdup rather than using kmalloc/kzalloc + memcpy.
Signed-off-by: Fuqian Huang <huangfq.daxian@gmail.com>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

drivers/media/usb/em28xx/em28xx-cards.c

@@ -3566,13 +3566,12 @@ static int em28xx_init_dev(struct em28xx *dev, struct usb_device *udev,
 static int em28xx_duplicate_dev(struct em28xx *dev)
 {
 	int nr;
-	struct em28xx *sec_dev = kzalloc(sizeof(*sec_dev), GFP_KERNEL);
+	struct em28xx *sec_dev = kmemdup(dev, sizeof(*sec_dev), GFP_KERNEL);
 
 	if (!sec_dev) {
 		dev->dev_next = NULL;
 		return -ENOMEM;
 	}
-	memcpy(sec_dev, dev, sizeof(*sec_dev));
 	/* Check to see next free device and mark as used */
 	do {
 		nr = find_first_zero_bit(em28xx_devused, EM28XX_MAXBOARDS);

drivers/media/usb/zr364xx/zr364xx.c

@@ -197,12 +197,10 @@ static int send_control_msg(struct usb_device *udev, u8 request, u16 value,
 {
 	int status;
 
-	unsigned char *transfer_buffer = kmalloc(size, GFP_KERNEL);
+	unsigned char *transfer_buffer = kmemdup(cp, size, GFP_KERNEL);
 	if (!transfer_buffer)
 		return -ENOMEM;
 
-	memcpy(transfer_buffer, cp, size);
-
 	status = usb_control_msg(udev,
 				 usb_sndctrlpipe(udev, 0),
 				 request,