raa489000: Sink VBUS before switching to TCPC side
raa489000: Sink VBUS before switching to TCPC side

When the RAA48900 switches from charger IC control to TCPC control, it
will disable the ASGATE.  In cases where the board is booted without a
battery, this can cause a loss in VSYS.  This commit has the board
attempt to sink VBUS if it's present prior to switching the part to
TCPC control.

BUG=b:181712325
BRANCH=dedede
TEST=Build and flash galith, remove battery, plug in 45W charger,
verify that DUT can boot up.

Signed-off-by: Aseda Aboagye <12c9b286316a940fd31c24070da5ab64cdd4d0e7@google.com>
Change-Id: Id5b3269911d3b8222b28886f66ef724e3e82c637
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2829115
Reviewed-by: Diana Z <cb2016afc7183e5356c690dc63b4ba817470501a@chromium.org>
Tested-by: Aseda Aboagye <12c9b286316a940fd31c24070da5ab64cdd4d0e7@chromium.org>
Commit-Queue: Aseda Aboagye <12c9b286316a940fd31c24070da5ab64cdd4d0e7@chromium.org>

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