thermal: adc_tm: Ensure drvdata is set for all adc_tm instances

For adc_tm instances of type iio, drvdata is not set before
exiting probe, which may lead to issues when dev_pm_ops are
used. Set drvdata for these adc_tm instances too.

Change-Id: If78162455abf44d3071a8816582262d776a12318
Signed-off-by: Jishnu Prakash <jprakash@codeaurora.org>