ifconfig.8: Improve -f synopsis
- There is no need to mention in the synopsis that -f can be a list of comma-separated type:format pairs. Let's keep it simple instead.
- Mention that -f can be supplied multiple times.
- Add -f to other entries in the synopsis where it can be used.
MFC after: 2 weeks
(cherry picked from commit 52ec8807d8b3a59b7497a3aa94952c7ad4b162bd)