ACPI / Battery: avoid acpi_battery_add() use-after-free

When acpi_battery_add_fs() fails the error handling code does not clean
up completely.  Moreover, it does not return resulting in a
use-after-free.

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Len Brown <len.brown@intel.com>