dahdi_dynamic: Close race on unload if red alarm timer was running when unloaded.

I saw a kernel oops that was the result of the timer running after the
dahdi_dynamic module was unloaded. Now we wait for the timer to complete, and
then delete it again in case it reactivated itself.

Signed-off-by: Shaun Ruffell <sruffell@digium.com>

git-svn-id: http://svn.asterisk.org/svn/dahdi/linux/trunk@10625 a0bf4364-ded3-4de4-8d8a-66a801d63aff

drivers/dahdi/dahdi_dynamic.c

@@ -857,6 +857,9 @@ static void dahdi_dynamic_cleanup(void)
 		tasklet_kill(&dahdi_dynamic_tlet);
 	}
 #endif
+	del_timer_sync(&alarmcheck);
+	/* Must call again in case it was running before and rescheduled
+	 * itself. */
 	del_timer(&alarmcheck);
 	printk(KERN_INFO "DAHDI Dynamic Span support unloaded\n");
 }