iio: chemical: bme680: Remove redundant gas configuration

iio: chemical: bme680: Remove redundant gas configuration

There is no need to explicitly configure the gas measurement registers
every time a gas measurement takes place. These are initial configurations
which are written in the beginning and they are not changed throughout
the lifetime of the driver.

If in the future, the device starts to support multiple configuration
profiles with variable heater duration and heater temperature, then they
could become members of the ->read_avail().

Signed-off-by: Vasileios Amoiridis <vassilisamir@gmail.com>
Link: https://patch.msgid.link/20240609233826.330516-14-vassilisamir@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>