Regenerate usb.conf

MFC after:	3 days


git-svn-id: svn+ssh://svn.freebsd.org/base/head@272253 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f
Instead of creating the full range of possible ports, try to figure
out the actual number of so-called "embedded jacks" which are present
when a USB MIDI device is attaching.

MFC after:	3 days


git-svn-id: svn+ssh://svn.freebsd.org/base/head@272254 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f