power: supply: charger-manager: fix incorrect health status

cm->emergency_stop will only be the value in the enumeration,
and cannot be less than zero, it will get an exception value.
So replace it with the corresponding value.

Signed-off-by: Junlin Yang <yangjunlin@yulong.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>