USB: ehci: fix some ehci hangs and crashes

I noticed that the "Refactor "if (handshake()) state = HC_STATE_HALT"
patch from earlier this year perpetuated a potential problem:  it can
mark the controller as halted when it's still running (but not acting
as, perhaps wrongly, expected).

That caused some hangs and crashes, rather than more polite failure
modes of a truly halted controller.  This patch forces a true halt,
and emits a (previously missing) diagnostic.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>