ACPI: Add stubs for wakeup handler functions

ACPI: Add stubs for wakeup handler functions

The commit d659c4c8aeac ("ACPI: PM: Add acpi_[un]register_wakeup_handler()")
added new functions for drivers to use during the s2idle wakeup path, but
didn't add stubs for when CONFIG_ACPI wasn't set.

Add those stubs in for other drivers to be able to use.

Fixes: d659c4c8aeac ("ACPI: PM: Add acpi_[un]register_wakeup_handler()")
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Link: https://lore.kernel.org/r/20211101014853.6177-1-mario.limonciello@amd.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>