[bridge STP] potential syntax error -> last_member_interval

For Developers
5

Might be a an actual code misrepresentation [bug], iproute2 (kernel ?) [4] would seem to expect

mcast_last_member_interval

[4] https://git.kernel.org/pub/scm/network/iproute2/iproute2.git/tree/ip/iplink_bridge.c#n53