usbconfig: use getopt(3) for option handling

[joerg]

Summary

This makes option handling consistent with other utilities as well as
Posix rules. By that, it's no longer important whether option name and
its argument are separated by a space or not, so -d5.3 works the same
as -d 5.3.

Also, recognize either /dev/ugen or ugen as prefix to the -d argument.

Note that this removes the undocumented feature that allowed to
specify multiple -d n.m options interleaved with commands referring to
that particular device in a single run.

[• hselasky]

Looks good.

usr.sbin/usbconfig/usbconfig.c

579

style: I think this line should have four spaces indentation from the "} else if "

[joerg]

Documentation fixes, mainly for -i option

• in usage(), clearly mark -i interface as optional
• both, -u busnum and -a devaddr are optional as well
• various minor man page fixes
• clearly mark those two commands that actually use -i ifaceidx
• remove unused bitfield tag got_iface
• fix indentation level according to review comment

[• hselasky]

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