oak: allow charging of dead battery requesting nil
oak: allow charging of dead battery requesting nil

On oak battery, when the battery is dead it reports 0 for desired
voltage, current, and state of charge. In this case we should allow
charging.

Added a CONFIG option for this that should be removed as soon as
the battery side is fixed.

With this CL, when a dead oak battery is used and a charger is
connected, we attempt to charge it.

BUG=chrome-os-partner:51454
BRANCH=none
TEST=test on an oak with a dead battery. w/o this CL, the battery
never charges because the charging not allowed flag is set. With this
CL, the battery charges.

Change-Id: If9f1250cd41aec265838e1d109f53c1bcd58c111
Signed-off-by: YH Huang <d2b6e71fb6119e288e33a854f7510c1046bfaea5@mediatek.com>
Reviewed-on: https://chromium-review.googlesource.com/334471
Reviewed-by: Rong Chang <3a05493f7adfb36d203f663b3bc2ba30e9d6284f@chromium.org>

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