iio: imu: adis: Remove adis_initial_startup function

Remove adis_initial_startup function since it is not used
anymore.

Signed-off-by: Ramona Bolboaca <ramona.bolboaca@analog.com>
Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20221122082757.449452-10-ramona.bolboaca@analog.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>