The new mpu3050 driver fails to build if I2C is disabled:

drivers/iio/built-in.o: In function `mpu3050_i2c_driver_exit':
mpu3050-i2c.c:(.exit.text+0x17f): undefined reference to `i2c_del_driver'
drivers/iio/built-in.o: In function `mpu3050_i2c_driver_init':
mpu3050-i2c.c:(.init.text+0x215): undefined reference to `i2c_register_driver'

This adds a Kconfig dependency to ensure we only build it when I2C
is available.

Fixes: 3904b28e ("iio: gyro: Add driver for the MPU-3050 gyroscope")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>