A temperature polling task is added to achieve temporal correction and
also reduce the latency of reading temperature.
Factor out sensor specific part to keep code clean.
Signed-off-by: Vic Yang <victoryang@chromium.org>
BUG=chrome-os-partner:7801
TEST=On link, 'temps' shows all temperature readings.
Cover each sensor with hand and see object temperature rise.
Compilation succeeded on bds/adv/daisy/discovery.
Change-Id: I3c44c8b2e3ab2aa9ce640d3fc25e7fba56534b86
