EHCI on armv6 with Write-Back caches

[Hans Petter Selasky]

Hi,

I've run some basic tests over here (x86) which passed after some patch 
modifications. Please test and verify for your ARM targets:

http://svnweb.freebsd.org/changeset/base/244500
http://svnweb.freebsd.org/changeset/base/244503

Please also verify that upgt and uwrt and uath still works like expected.

--HPS