EDAC: Rework workqueue handling

Hide the EDAC workqueue pointer in a separate compilation unit and add
accessors for the workqueue manipulations needed.

Remove edac_pci_reset_delay_period() which wasn't used by anything. It
seems it got added without a user with

  91b99041c1 ("drivers/edac: updated PCI monitoring")

Signed-off-by: Borislav Petkov <bp@suse.de>

drivers/edac/edac_module.h

@@ -47,7 +47,12 @@ extern int edac_device_create_sysfs(struct edac_device_ctl_info *edac_dev);
 extern void edac_device_remove_sysfs(struct edac_device_ctl_info *edac_dev);
 
 /* edac core workqueue: single CPU mode */
-extern struct workqueue_struct *edac_workqueue;
+int edac_workqueue_setup(void);
+void edac_workqueue_teardown(void);
+bool edac_queue_work(struct delayed_work *work, unsigned long delay);
+bool edac_stop_work(struct delayed_work *work);
+bool edac_mod_work(struct delayed_work *work, unsigned long delay);
+
 extern void edac_device_reset_delay_period(struct edac_device_ctl_info
 					   *edac_dev, unsigned long value);
 extern void edac_mc_reset_delay_period(unsigned long value);