trace: remove code that depends on setting vcpu

trace: remove code that depends on setting vcpu

Now we no longer have any events that are for vcpus we can start
excising the code from the trace control. As the vcpu parameter is
encoded as part of QMP we just stub out the has_vcpu/vcpu parameters
rather than alter the API.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-id: 20230526165401.574474-8-alex.bennee@linaro.org
Message-Id: <20230524133952.3971948-7-alex.bennee@linaro.org>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>