ACPI / hotplug / PCI: Consolidate slot disabling and ejecting

Both acpiphp_disable_slot() and acpiphp_eject_slot() are always
called together so instead of calling each separately we can
consolidate them into one function acpiphp_disable_and_eject_slot()
that does both (but it will return success on _EJ0 failures that
were ignored in the majority of call sites anyway).

[rjw: Rebased plus minor tweaks]
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>