sensor: lis2dw12: handle `SENSOR_CHAN_ALL` in `sample_fetch` callback

Handle `SENSOR_CHAN_ALL` case of the sample_fetch callback of the
lis2dw12 driver. Without this, `sensor_sample_fetch()` does not work
correctly for this device, e.g. rendering the rtio and the sensor shell
unusable.

Signed-off-by: Ruben Völl <ruben.voell@sevenlab.de>