net: dsa: fix NULL pointer dereference in dsa_port_reset_vlan_filtering

In the Linux kernel, the following vulnerability has been resolved: net: dsa: fix NULL pointer dereference in dsa_port_reset_vlan_filtering The "ds" iterator variable used in dsa_port_reset_vlan_filtering() -> dsa_switch_for_each_port() overwrites the "dp" received as argument, which is later used to call dsa_port_vlan_filtering() proper. As a result, switches which do enter that code path (the ones with vlan_filtering_is_global=true) will dereference an invalid dp in dsa_port_reset_vlan_filtering() after leaving a VLAN-aware bridge. Use a dedicated "other_dp" iterator variable to avoid this from happening.