tcpm/fusb302: Update VBUS supplier when VBUS level changes
tcpm/fusb302: Update VBUS supplier when VBUS level changes

To enable USB charging on boards where fusb302 takes care of VBUS detection

BUG=b:65446459
BRANCH=none
TEST=on Scarlet rev3, verify VBUS supplier is updated based on
whether VBUS is present - plug/unplug USB2 charger, boot with USB2
charger plugged.

Change-Id: I50177d40b0eb0490634ad2f103306e0079633fbe
Signed-off-by: Philip Chen <3ee404f9ef892bc3fda6e6a76e65843b5fa44db2@google.com>
Reviewed-on: https://chromium-review.googlesource.com/905401
Commit-Ready: Philip Chen <3ee404f9ef892bc3fda6e6a76e65843b5fa44db2@chromium.org>
Tested-by: Philip Chen <3ee404f9ef892bc3fda6e6a76e65843b5fa44db2@chromium.org>
Reviewed-by: Nicolas Boichat <f3daba1cdc403799935674d3cd4b0e5bd1804232@chromium.org>

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