media: siano: Use kmemdup instead of duplicating its function

kmemdup has implemented the function that kmalloc() + memcpy().
We prefer to kmemdup rather than code opened implementation.

This issue was detected with the help of coccinelle.
Signed-off-by: Wen Yang <wen.yang99@zte.com.cn>
CC: Tomoki Sekiyama <tomoki.sekiyama@gmail.com>
CC: linux-kernel@vger.kernel.org
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

drivers/media/usb/siano/smsusb.c

@@ -225,10 +225,9 @@ static int smsusb_sendrequest(void *context, void *buffer, size_t size)
 		return -ENOENT;
 	}
 
-	phdr = kmalloc(size, GFP_KERNEL);
+	phdr = kmemdup(buffer, size, GFP_KERNEL);
 	if (!phdr)
 		return -ENOMEM;
-	memcpy(phdr, buffer, size);
 
 	pr_debug("sending %s(%d) size: %d\n",
 		  smscore_translate_msg(phdr->msg_type), phdr->msg_type,