iio: chemical: bme680: Move forced mode setup in ->read_raw()

Whenever the sensor is set to forced mode, a TPHG cycle is triggered and
the values of temperature, pressure, humidity and gas become ready to be
read.

The setup of the forced mode to trigger measurements was located inside
the read_{temp/gas}() functions. This was not posing a functional problem
since read_{humid/press}() are internally calling read_temp() so the
forced mode is set through this call.

This is not very clear and it is kind of hidden that regardless of the
measurement, the setup of the forced mode needs to happen before any
measurement.

Signed-off-by: Vasileios Amoiridis <vassilisamir@gmail.com>
Link: https://patch.msgid.link/20240609233826.330516-15-vassilisamir@gmail.com


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