mesh: add frags to bt_mesh_adv struct
bt_mesh_adv was lacking frags member. It was left out in few places or
wrongly interpreted as "flags", causing the typo.
diff --git a/nimble/host/mesh/src/adv.h b/nimble/host/mesh/src/adv.h
index 38db786..6dd2c81 100644
--- a/nimble/host/mesh/src/adv.h
+++ b/nimble/host/mesh/src/adv.h
@@ -35,8 +35,8 @@
 				   int err, void *user_data);
 
 struct bt_mesh_adv {
-
-	struct net_buf *frags;
+	/** Fragments associated with this buffer. */
+	struct os_mbuf *frags;
 
 	const struct bt_mesh_send_cb *cb;
 	void *cb_data;
diff --git a/nimble/host/mesh/src/friend.c b/nimble/host/mesh/src/friend.c
index 354d31a..4742e89 100644
--- a/nimble/host/mesh/src/friend.c
+++ b/nimble/host/mesh/src/friend.c
@@ -1236,7 +1236,7 @@
 
 	/* Clear the flag we use for segment tracking */
 	BT_MESH_ADV(frnd->last)->flags &= ~NET_BUF_FRAGS;
-	BT_MESH_ADV(frnd->last)->frags = 0;
+	BT_MESH_ADV(frnd->last)->frags = NULL;
 
 	BT_DBG("Sending buf %p from Friend Queue of LPN 0x%04x",
 	       frnd->last, frnd->lpn);
@@ -1382,8 +1382,8 @@
 
 			net_buf_slist_remove(&frnd->queue, prev, cur);
 			frnd->queue_size--;
-			BT_MESH_ADV(buf)->frags = 0;
-
+			/* Make sure old slist entry state doesn't remain */
+			BT_MESH_ADV(buf)->frags = NULL;
 			net_buf_unref(buf);
 			break;
 		}