media: usbvision: Improve a size determination in usbvision_alloc()

Replace the specification of a data structure by a pointer dereference
as the parameter for the operator "sizeof" to make the corresponding size
determination a bit safer according to the Linux coding style convention.

This issue was detected by using the Coccinelle software.
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/usb/usbvision/usbvision-video.c

@@ -1319,7 +1319,7 @@ static struct usb_usbvision *usbvision_alloc(struct usb_device *dev,
 {
 	struct usb_usbvision *usbvision;
 
-	usbvision = kzalloc(sizeof(struct usb_usbvision), GFP_KERNEL);
+	usbvision = kzalloc(sizeof(*usbvision), GFP_KERNEL);
 	if (!usbvision)
 		return NULL;