ohci: drop computed flags from trace events

This exceeded the trace argument limit for LTTNG UST and wasn't really
needed as the flags value is stored anyway. Dropping this fixes the
compile failure for UST. It can probably be merged with the previous
trace shortening patch.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
