# DF-3279 — struct bridge_ifinfo leaked on every span-port delete

## What

`bridge_ioctl_addspan()` allocates a `bridge_ifinfo` for the span bif
(if_bridge.c:1823-1828), but `bridge_delete_span()` frees only the
bif (if_bridge.c:1155-1156) — the `bif_info` is never freed.  Every
spanport add/del cycle leaks ~114-120 bytes of M_DEVBUF kernel memory.

## Reproduce (guest, as root)

```
cd /root/poc/df-3279
cc -O -o span_leak span_leak.c
# create bridge0 + tap0 first
./span_leak 20000
vmstat -m | grep devbuf
```

## Expected

devbuf in-use grows by ~2.3 MB after 20000 cycles (measured:
3.12M -> 5.40M, i.e. ~114 bytes/cycle).