battery-gb: Allow kernel values to get out of sync with greybus spec

We can't know that the greybus values and the kernel values for a number
of battery enumerated types will remain in sync.  And as theses are sent
by an external device from the kernel, we have to explicitly check these
values.

Reported-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>