eldrid: fix customized thermal policy
eldrid: fix customized thermal policy

Fix fan rpm won't change when DUT cool down.
Because current_level will equal to num_fan_levels when temperature reach to the highest level.

BUG=b:176875592
BRANCH=firmware-volteer-13672.B-main
TEST=make buildall
TEST=make sure fan will speed down when DUT cool down.

Signed-off-by: Scott Chao <8cefa9751fac9aaa897ba1213763a96ba8dbd20d@wistron.corp-partner.google.com>
Change-Id: I2e4c55e103674a35690ce2f9360a976afe624a2a
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2612242
Reviewed-by: Keith Short <f6d578f97033c25f1206cb57d52f358974c82954@chromium.org>

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