usb_charger: Always update VBUS charge supplier
usb_charger: Always update VBUS charge supplier

usb_charger_init() did not call charge_manager_update_charge() if we are
sourcing VBUS. This means we can get stuck with charge_manager_is_seeded()
never returning true, and so charging never starts, and power-on is
prevented.

Change update_vbus_supplier() so it always calls
charge_manager_update_charge(), but with current = 0 when we are sourcing
VBUS.

BUG=b:80203727
BRANCH=none
TEST=Reboot Grunt EC while one USB-C port is VBUS source.

Change-Id: I24c29dc6b9ad9c50254181614a6440d2d055cd5a
Signed-off-by: Edward Hill <db1406b34e091703092b6b136bdfeb2c8125fc0e@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1086113
Commit-Ready: ChromeOS CL Exonerator Bot <fa429e5907f00867f797423aea74327bb02c91b6@appspot.gserviceaccount.com>
Reviewed-by: Aseda Aboagye <12c9b286316a940fd31c24070da5ab64cdd4d0e7@chromium.org>
Reviewed-by: Jett Rink <9d4aef0593e6843318d99df31597fb6153b89787@chromium.org>

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