CAM: Keep periph_links when restoring CCB in camperiphdone().

While recovery command executed, some other commands from the periph
may complete, that may affect periph_links of this CCB.  So restoring
original CCB we must keep current periph_links as more up to date.

I've found this triggering assertions with debug kernel and suspect
some memory corruptions otherwise when spun down disk receives two
or sometimes more concurrent requests.

MFC after:	1 week
Sponsored by:	iXsystems, Inc.

sys/cam/cam_periph.c

@@ -1435,11 +1435,6 @@ camperiphdone(struct cam_periph *periph, union ccb *done_ccb)
 	 * blocking by that also any new recovery attempts for this CCB,
 	 * and the result will be the final one returned to the CCB owher.
 	 */
-
-	/*
-	 * Copy the CCB back, preserving the alloc_flags field.  Things
-	 * will crash horribly if the CCBs are not of the same size.
-	 */
 	saved_ccb = (union ccb *)done_ccb->ccb_h.saved_ccb_ptr;
 	KASSERT(saved_ccb->ccb_h.func_code == XPT_SCSI_IO,
 	    ("%s: saved_ccb func_code %#x != XPT_SCSI_IO",
@@ -1447,6 +1442,7 @@ camperiphdone(struct cam_periph *periph, union ccb *done_ccb)
 	KASSERT(done_ccb->ccb_h.func_code == XPT_SCSI_IO,
 	    ("%s: done_ccb func_code %#x != XPT_SCSI_IO",
 	     __func__, done_ccb->ccb_h.func_code));
+	saved_ccb->ccb_h.periph_links = done_ccb->ccb_h.periph_links;
 	done_flags = done_ccb->ccb_h.alloc_flags;
 	bcopy(saved_ccb, done_ccb, sizeof(struct ccb_scsiio));
 	done_ccb->ccb_h.alloc_flags = done_flags;