staging: pi433: Split subtraction across 2 lines

Split a subtraction across 2 lines in order to make these lines
no longer than 80 columns. Problem found with checkpatch.
Signed-off-by: Eisha Chen-yen-su <chenyensu0@gmail.com>
Acked-by: Julia Lawall <julia.lawall@lip6.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/pi433/pi433_if.c

@@ -528,7 +528,8 @@ pi433_receive(void *data)
 
 		/* need to drop bytes or acquire? */
 		if (dev->rx_bytes_to_drop > dev->rx_bytes_dropped)
-			bytes_to_read = dev->rx_bytes_to_drop - dev->rx_bytes_dropped;
+			bytes_to_read = dev->rx_bytes_to_drop -
+					dev->rx_bytes_dropped;
 		else
 			bytes_to_read = bytes_total - dev->rx_position;