Make LACP based lagg work with interfaces (like 100Gbps and 25Gbps) that
report extended media types.

lacp_aggregator_bandwidth() uses the media to determine the speed of the
interface and returns 0 for IFM_OTHER without the bits in the extended
range.

Reported by: kbowling@
Reviewed by: eugen_grosbein.net, mjoras@
MFC after: 1 week
Sponsored by: Chelsio Communications
Differential Revision: https://reviews.freebsd.org/D12188