ACPI: battery: Don't return -EFAIL on broken packages.

Acer BIOS has a bug which is exposed when a dead battery is present.

The package template that is used to describe battery status is
over-written with sane values when the battery is live.
But when the batter is dead, a bogus reference in the template
is used.  In this case, Linux returns a fault, when instead
it should simply return that it doesn't know the missing value.

http://bugzilla.kernel.org/show_bug.cgi?id=8573
http://bugzilla.kernel.org/show_bug.cgi?id=10202

Signed-off-by: Alexey Starikovskiy <astarikovskiy@suse.de>
Signed-off-by: Len Brown <len.brown@intel.com>