i2cbus: remove unused dev field

The dev field in i2cbus is not used.
So just drop it.

Signed-off-by: KONRAD Frederic <fred.konrad@greensocs.com>
Reviewed-by: Alistair Francis <alistair.francis@xilinx.com>
Reviewed-by: Peter Crosthwaite <crosthwaite.peter@gmail.com>
Tested-By: Hyun Kwon <hyun.kwon@xilinx.com>
Message-id: 1465833014-21982-2-git-send-email-fred.konrad@greensocs.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

hw/i2c/core.c

@@ -14,7 +14,6 @@ struct I2CBus
 {
     BusState qbus;
     I2CSlave *current_dev;
-    I2CSlave *dev;
     uint8_t saved_address;
 };