ACPI / hotplug: Fix PCI host bridge hot removal

Since the PCI host bridge scan handler does not set hotplug.enabled,
the check of it in acpi_bus_device_eject() effectively prevents the
root bridge hot removal from working after commit a3b1b1ef
(ACPI / hotplug: Merge device hot-removal routines).  However, that
check is not necessary, because the other acpi_bus_device_eject()
users, acpi_hotplug_notify_cb and acpi_eject_store(), do the same
check by themselves before executing that function.

For this reason, remove the scan handler check from
acpi_bus_device_eject() to make PCI hot bridge hot removal work
again.

Fixes: a3b1b1ef (ACPI / hotplug: Merge device hot-removal routines)
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Toshi Kani <toshi.kani@hp.com>