thermal: Don't send thermal warning while in G3
thermal: Don't send thermal warning while in G3

There may be certain states when temperature sensors can't be
read. For instance a thermistor circuit could be tied to a power rail
that is only up when the AP is out of G3. In the function
thermal_control when there are no sensors read, it's calling a
function that adds a warning message to the EC log and sets a host
event. If the AP is in G3.

This CL adds a check for chipset state to guard against adding EC log
messages when it would be an expected state.

BUG=b:123297357
BRANCH=none
TEST=Forced AP into G3 with 'aps' and verified that the log message
"can't read any temp sensors!" is no longer being generated.

Change-Id: Id4d73f58e1d3a6d3c24b9888b385cc5e6f803782
Signed-off-by: Scott Collyer <7d40b3eb9e17bf55d972074a5e77a7ea4159f9dd@google.com>
Reviewed-on: https://chromium-review.googlesource.com/1481405
Commit-Ready: Scott Collyer <7d40b3eb9e17bf55d972074a5e77a7ea4159f9dd@chromium.org>
Tested-by: Scott Collyer <7d40b3eb9e17bf55d972074a5e77a7ea4159f9dd@chromium.org>
Reviewed-by: Daisuke Nojiri <fd5f93af191bf7e8f73ea71cc3c0f66b41b1dd49@chromium.org>
Reviewed-by: Furquan Shaikh <6be5c96c464778f89679b1062a2e0a6af93d2aa5@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec