PCI/ACPI: acpiphp: Rename alloc_acpiphp_hp_work() to alloc_acpi_hp_work()

Will need to use it for PCI root bridge hotplug support, so rename
*acpiphp* to *acpi* and move to osc.c.  Also make kacpi_hotplug_wq static
after that.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
CC: Len Brown <lenb@kernel.org>
CC: linux-acpi@vger.kernel.org

include/acpi/acpiosxf.h

@@ -193,8 +193,6 @@ void acpi_os_fixed_event_count(u32 fixed_event_number);
 /*
  * Threads and Scheduling
  */
-extern struct workqueue_struct *kacpi_hotplug_wq;
-
 acpi_thread_id acpi_os_get_thread_id(void);
 
 acpi_status