a Set TR
dequeue pointer command.

It turns out that the NEC host controllers can handle active TRBs being
set to no-op TRBs after a stop endpoint command, but other host
controllers have issues with this out-of-spec software behavior.  Fix this
behavior.

This patch should be backported to kernels as far back as 2.6.31, but it
may be a bit challenging, since process_ctrl_td() was introduced in some
refactoring done in 2.6.36, and some endian-safe patches added in 2.6.40
that touch the same lines.

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: stable@kernel.org
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