dcmi: get temperature readings: read temp sensors

This commit adds the code to read temperatures from various sensors. A
JSON config file tells what D-Bus object(s) to look up for a specific
temperature reading.

Resolves openbmc/openbmc#2626

Change-Id: Ic357ec2a53ff250a2517d68defe5850ef353568a
Signed-off-by: Deepak Kodihalli <dkodihal@in.ibm.com>
2 files changed