ACPI / battery: Fix incorrect sscanf() string in acpi_battery_init_alarm()

Fix incorrect sscanf() string in acpi_battery_init_alarm().
Change from %ld to %lu, because 'x' is unsigned long.

Signed-off-by: Luis G.F <luisgf@luisgf.es>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>