If CONFIG_I2C is m and CONFIG_I2C_SLAVE is y,
building with CONFIG_IPMB_DEVICE_INTERFACE setting to
y will fail:

drivers/char/ipmi/ipmb_dev_int.o: In function `ipmb_remove':
ipmb_dev_int.c: undefined reference to `i2c_slave_unregister'
drivers/char/ipmi/ipmb_dev_int.o: In function `ipmb_write':
ipmb_dev_int.c: undefined reference to `i2c_smbus_write_block_data'
drivers/char/ipmi/ipmb_dev_int.o: In function `ipmb_probe':
ipmb_dev_int.c: undefined reference to `i2c_slave_register'
drivers/char/ipmi/ipmb_dev_int.o: In function `ipmb_driver_init':
ipmb_dev_int.c: undefined reference to `i2c_register_driver'
drivers/char/ipmi/ipmb_dev_int.o: In function `ipmb_driver_exit':
ipmb_dev_int.c: undefined reference to `i2c_del_driver'

Add I2C Kconfig dependency to fix this.
Reported-by: Hulk Robot <hulkci@huawei.com>
Fixes: 51bd6f29 ("Add support for IPMB driver")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Message-Id: <20190612031825.24732-1-yuehaibing@huawei.com>
Signed-off-by: Corey Minyard <cminyard@mvista.com>