ACPI / dock: Drop unnecessary local variable from dock_add()

The local variable id in dock_add() is not necessary, so drop it.

While we're at it, use an initializer to clear the local variable ds
and drop the memset() used for this purpose.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Merge branch 'acpi-cleanup-next' into bleeding-edge

* acpi-cleanup-next:
  ACPI / dock: Drop unnecessary local variable from dock_add()
  ACPI / dock / PCI: Drop ACPI dock notifier chain
  ACPI / dock: Do not check CONFIG_ACPI_DOCK_MODULE
  ACPI / dock: Do not leak memory on falilures to add a dock station
  ACPI: Drop ACPI bus notifier call chain
  ACPI / dock: Rework the handling of notifications
  ACPI / dock: Simplify dock_init_hotplug() and dock_release_hotplug()
  ACPI / dock: Walk list in reverse order during removal of devices
  ACPI / dock: Rework and simplify find_dock_devices()
  ACPI / dock: Drop the hp_lock mutex from struct dock_station
  ACPI: simplify acpiphp driver with new helper functions
  ACPI: simplify dock driver with new helper functions
  ACPI: Export acpi_(bay)|(dock)_match() from scan.c
  ACPI: introduce two helper functions for _EJ0 and _LCK
  ACPI: introduce helper function acpi_execute_simple_method()
  ACPI: introduce helper function acpi_has_method()
  ACPI / dock: simplify dock_create_acpi_device()
  ACPI / dock: mark initialization functions with __init
  ACPI / dock: drop redundant spin lock in dock station object
  ACPI / dock: avoid initializing acpi_dock_notifier_list multiple times