temp_metrics: tmp006 calibration and fan loop updates
temp_metrics: tmp006 calibration and fan loop updates

With the recent changes that have gone into the EC, the TMP006
calibration data is no longer present in the EC by default. Push it down
to the EC via the newly added ectool tmp006cal command.

Also added couple of changes to the fan loop:
- hand back fan control loop to the EC if none of the TMP006 sensors
  report valid temperatures.
- handle S0->S3->S0 transition where the EC sets the fan to 0 RPM.

BUG=chrome-os-partner:9193
TEST=run "ectool tmp006cal" command for sensors 0, 1, 2 and 3 and ensure
that they return non-zero calibration values.
BRANCH=none

Change-Id: Iaf91216a4d3353f15489b39aba9acb34055551cf
Signed-off-by: Sameer Nanda <3daf6939ed4518939423e49b8a1025b098597787@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/35469
Reviewed-by: Vincent Palatin <70a9964ec8fd10b0b08fcc8623c2add25ddf99ac@chromium.org>
Reviewed-by: Todd Broch <035f5b1f817cbb94019cec357b99778115602b63@chromium.org>

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