ACPI: battery: check result of register_pm_notifier()

This function call can fail, check for that.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Link: https://patch.msgid.link/20240904-acpi-battery-cleanups-v1-1-a3bf74f22d40@weissschuh.net


Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>