iio: temperature: tmp006: make sure the chip is powered up in probe

iio: temperature: tmp006: make sure the chip is powered up in probe

When the device is probed, there's no guarantee that the device is not in
power-down mode. This can happen if the driver is unregistered and
re-probed.

To make sure this doesn't happen, the value of the TMP006_CONFIG register
(which is read in the probe function and stored in the device's private
data) is being checked to see if the MOD bits have the correct value.

This is a fix for a somewhat-rare corner case. As it stands, this doesn't
look like a high priority to go into the Fixes route.

Signed-off-by: Alexandru Ardelean <aardelean@deviqon.com>
Link: https://lore.kernel.org/r/20210624081924.15897-2-aardelean@deviqon.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>