USB: disable rust bindings from the build for now

The rust USB bindings as submitted are a good start, but they don't
really seem to be correct in a number of minor places, so just disable
them from the build entirely at this point in time.  When they are ready
to be re-enabled, this commit can be reverted.

Acked-by: Daniel Almeida <daniel.almeida@collabora.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>