usb4bsd: Remove an obsolete comment in a Makefile.
usbconfig.8: Add a usbdump(8) reference.
Add some USB serial driver manpages from FreeBSD.

u3g(4)
ubser(4)
ucycom(4)
uipaq(4)
umcs(4)
tcp: Remove unused code
usb4bsd: Add back the ID for HandyTech's Braille displays to ubsa(4).

See fb55151b494cf8878797ecfa6429d34f3a757765 where it was added
to our old obsa(4).

Also sync the manual page with FreeBSD.
Sync some USB serial driver manual pages with FreeBSD.

uark(4)
uchcom(4)
uftdi(4)
ulpt(4)
umct(4)
umodem(4)
Sync uvisor.4 and uvscom.4 with FreeBSD.