How to specify userconf kernel options on armv7

[Mayuresh <mayuresh%acm.org@localhost>]

On device:

# uname -a
NetBSD pi 8.0_RC1 NetBSD 8.0_RC1 (RPI2.201804240813Z) evbarm

I wish to enable ugen interface, to use a USB scanner. The device is
getting detected as ulpt instead.

I checked the kernel conf, in which both ulpt and ugen are enabled. I
think disabling ulpt module would make it detect as ugen.

One way is to recompile the kernel disabling ulpt. But I read the
documentation and find an option like userconf=disable ulpt*.

But on above architecture I do not find boot.cfg. Instead I noticed
cmdline.txt. Could not find much documentation on cmdline.txt though.

What is the right way to disable ulpt* on above architecture?

Mayuresh