iio: imu: inv_mpu6050: simplify code in write_event_config callback

iio: imu: inv_mpu6050: simplify code in write_event_config callback

iio_ev_state_store is actually using kstrtobool to check user
input, then gives the converted boolean value to the write_event_config
callback.

Remove useless code in write_event_config callback.

Signed-off-by: Julien Stephan <jstephan@baylibre.com>
Acked-by: Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@tdk.com>
Link: https://patch.msgid.link/20241024-iio-fix-write-event-config-signature-v1-5-7d29e5a31b00@baylibre.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>