Recent newbus lock patches cleanup in USB regard

[Hans Petter Selasky]

Hi,

I've reviewed Attilio's patches in USB regard and I've spent some hours today 
to cleanup his initial patch.

Result is below:

http://perforce.freebsd.org/chv.cgi?CH=167087

Patch for -current will be posted later. The patch needs some more testing 
before committing.

--HPS