misc: nct1008: change overheat enable message

misc: nct1008: change overheat enable message

Avoid using the word 'warning' in the log message that reports
successful setup of the overheat warning message. This confuses
tests that scan for errors and warnings on console.

Also changed the level of the message to pr_debug.

Bug 1436329

Change-Id: Idbc6cc5eed42265a1487a9809969bce7edc7a620
Signed-off-by: Diwakar Tundlam <dtundlam@nvidia.com>
Reviewed-on: http://git-master/r/378669
Reviewed-by: Bitan Biswas <bbiswas@nvidia.com>
Tested-by: Bitan Biswas <bbiswas@nvidia.com>