net: bridge: mst: pass vlan group directly to br_mst_vlan_set_state

In the Linux kernel, the following vulnerability has been resolved: net: bridge: mst: pass vlan group directly to br_mst_vlan_set_state Pass the already obtained vlan group pointer to br_mst_vlan_set_state() instead of dereferencing it again. Each caller has already correctly dereferenced it for their context. This change is required for the following suspicious RCU dereference fix. No functional changes intended.