ACPI / hotplug / PCI: Simplify acpi_install_hotplug_notify_handler()

Since acpi_hotplug_notify_cb() does not use its data argument any
more, the second argument of acpi_install_hotplug_notify_handler()
can be dropped, so do that and update its callers accordingly.

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