Regenerate the list of generated symbols for libifconfig:

```
grep -hr ^ifconfig_sfp_ /usr/obj/usr/src/amd64.amd64/lib/libifconfig \
| sed 's/(.*/;/' | sort -u
```

Spotted by build failures caused by a missing symbol while working on
upgrading libifconfig from internal to private.

Reviewed by:	markj
Differential Revision:	https://reviews.freebsd.org/D28927