dlm: eliminate astparam type casting

Put lkb_astparam in a union with a dlm_user_args pointer to
eliminate a lot of type casting.

Signed-off-by: David Teigland <teigland@redhat.com>
diff --git a/fs/dlm/memory.c b/fs/dlm/memory.c
index f778386..65e41e5 100644
--- a/fs/dlm/memory.c
+++ b/fs/dlm/memory.c
@@ -80,7 +80,7 @@
 {
 	if (lkb->lkb_flags & DLM_IFL_USER) {
 		struct dlm_user_args *ua;
-		ua = (struct dlm_user_args *)lkb->lkb_astparam;
+		ua = lkb->lkb_ua;
 		if (ua) {
 			if (ua->lksb.sb_lvbptr)
 				kfree(ua->lksb.sb_lvbptr);