ACPI / battery: move some ACPI_BATTERY_* definitions to header

ACPI_BATTERY_CLASS is used in multiple places.
Also, I'll use ACPI_BATTERY_NOTIFY_STATUS inside AC driver in
one of following patches.

So, create a header file and move ACPI_BATTERY_CLASS and
ACPI_BATTERY_NOTIFY_* definitions into it.
Also, remove copy of ACPI_BATTERY_CLASS from sbs.c

Signed-off-by: Alexander Mezin <mezin.alexander@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>