target/iscsi: Remove macros that contain typecasts

These just want to return a pointer instead of a value, but are otherwise
the same.

ISCSI_TPG_LUN macro was unused.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andy Grover <agrover@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c
index 35b61f7..934b5b9 100644
--- a/drivers/target/iscsi/iscsi_target.c
+++ b/drivers/target/iscsi/iscsi_target.c
@@ -4376,7 +4376,7 @@
 
 int iscsit_close_session(struct iscsi_session *sess)
 {
-	struct iscsi_portal_group *tpg = ISCSI_TPG_S(sess);
+	struct iscsi_portal_group *tpg = sess->tpg;
 	struct se_portal_group *se_tpg = &tpg->tpg_se_tpg;
 
 	if (atomic_read(&sess->nconn)) {