ice.4: Improve SYNOPSIS

[ziaee]

Summary

Remove prose from synopsis, adding sysctls and tunables. I would like
to use something standard across the manual for "substitute a number
here". We used to, and OtherBSDs do, just use ?, which is a standard
UNIX notation for a substitutable character. Our manual uses a mix of
Ns, ?s, and #s.

MFC after: 3 days

[ziaee]

We also need to fix the HARDWARE section. Supported hardware, and really only supported hardware, needs to be in there. Then, the entire section appears in the hardware compatibility list:

https://www.freebsd.org/releases/15.0R/hardware/

So, supported adapters needs to move from DESCRIPTION into HARDWARE, and information about configuring optics needs to go from HARDWARE to DESCRIPTION.

[kbowling]

The deletions seem fine. The convention is probably up to you if you are changing to this.