staging: comedi: jr3_pci: check sizes at compile time

The driver currently checks the size of `struct jr3_sensor` is correct
when a device is attached, returning an error if it is wrong.  Replace
that with a compile-time check.  We don't care too much about the size
of `struct jr3_sensor` as it is embedded in the larger `struct
jr3_block` and is followed by a lot of padding.  We should care more
that the size of `struct jr3_block` is correct, as it describes the
overall register layout of a block, and there is an array of such blocks
(one per subdevice).  Check its size at compile-time using the
`BUILD_BUG_ON()` macro.
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/drivers/jr3_pci.c

@@ -688,12 +688,7 @@ static int jr3_pci_auto_attach(struct comedi_device *dev,
 	int ret;
 	int i;
 
-	if (sizeof(struct jr3_sensor) != 0xc00) {
-		dev_err(dev->class_dev,
-			"sizeof(struct jr3_sensor) = %x [expected %x]\n",
-			(unsigned int)sizeof(struct jr3_sensor), 0xc00);
-		return -EINVAL;
-	}
+	BUILD_BUG_ON(sizeof(struct jr3_block) != 0x80000);
 
 	if (context < ARRAY_SIZE(jr3_pci_boards))
 		board = &jr3_pci_boards[context];