MFC r199058

MFC r199058

 Integrate lost interrupts patch from the old USB stack.

 Some EHCI chips from VIA / ATI seem to trigger interrupts before writing back
 the qTD status, or miss signalling occasionally under heavy load.  If the host
 machine is too fast, we can miss transaction completion - when we scan the
 active list the transaction still seems to be active. This generally exhibits
 itself as a umass stall that never recovers.

 We work around this behaviour by setting up this callback after any softintr
 that completes with transactions still pending, giving us another chance to
 check for completion after the writeback has taken place

Submitted by:	Alexander Nedotsuko

git-svn-id: svn://svn.freebsd.org/base/stable/8@199166 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f