pd: send power change event to AP whenever input power is changed

Send power change event to AP whenever input power is changed,
ensure that AP gets the latest power charging info.

BUG=chrome-os-partner:47677
BRANCH=none
TEST=tested on Oak by plug/unplug AC adapter to type-C ports and
verifying the UI battery icon shows the correct status instantly.

Change-Id: I7465afcd8bc9b1c56ecf70fc74446866a8ab1b9a
Signed-off-by: Ben Lok <ben.lok@mediatek.com>
Reviewed-on: https://chromium-review.googlesource.com/313926
Reviewed-by: Alec Berg <alecaberg@chromium.org>
5 files changed