edac: use to_delayed_work()

The edac-core driver includes code which assumes that the work_struct
which is included in every delayed_work is the first member of that
structure.  This is currently the case but might change in the future, so
use to_delayed_work() instead, which doesn't make such an assumption.

linux-2.6.30-rc1 has the to_delayed_work() function that will allow this
patch to work

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Doug Thompson <dougthompson@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/edac/edac_mc.c

@@ -260,7 +260,7 @@ static int edac_mc_assert_error_check_and_clear(void)
  */
 static void edac_mc_workq_function(struct work_struct *work_req)
 {
-	struct delayed_work *d_work = (struct delayed_work *)work_req;
+	struct delayed_work *d_work = to_delayed_work(work_req);
 	struct mem_ctl_info *mci = to_edac_mem_ctl_work(d_work);
 
 	mutex_lock(&mem_ctls_mutex);