nipperkin: Override current limit when no battery
nipperkin: Override current limit when no battery

When there is no battery or battery is malfunctioning, override charger
current limit to be 6A to prevent brownouts during boot.

BUG=b:202754460
BRANCH=guybrush
TEST=100+ cycles on R7 with 16GB
25% brownout with 65W charger without override.
15% brownout with 87W charger without override.
3% brownout with 65W charger with override.
0% brownout with 87W charger with override.

Change-Id: Ib8f1610415e6b185e694e07e048d15c4b6e8ffa5
Signed-off-by: Rob Barnes <3ced0940a2329ce70499686f01d3d60685ec66ed@google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3436689
Reviewed-by: Zick Wei <3d0b14a1e83601e71d11cd2c38ee93ff1dbbc737@quanta.corp-partner.google.com>
Reviewed-by: Diana Z <cb2016afc7183e5356c690dc63b4ba817470501a@chromium.org>

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