fuel_gauge: Remove status from fuel gauge properties

Based on review of the similar charger driver API, it's been demonstrated
from the community that embedding a per value status code when fetching
multiple properties isn't particularly wanted or needed. It was largely
considered not worth the additional maintenance to have the extra per
property error information.

Remove the status field from the fuel_gauge property value structs.

Signed-off-by: Aaron Massey <aaronmassey@google.com>