iio: inv_mpu6050: Remove superfluous indio_dev->modes assignment

iio: inv_mpu6050: Remove superfluous indio_dev->modes assignment

The inv_mpu6050 driver manually assigns the indio_dev->modes property. But
this is not necessary since it will be setup in iio_trigger_buffer_setup().

Remove the manual assignment.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Jean-Baptiste Maneyrol <jmaneyrol@invensense.com>
Link: https://lore.kernel.org/r/20210325131046.13383-1-lars@metafoo.de
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>