util/u_trace: add end_of_pipe property to tracepoints

util/u_trace: add end_of_pipe property to tracepoints

In order to capture the timestamp when things actually end on Intel
GPU HW, we need to know whether the timestamp should be capture at the
top or end of pipeline.

v2: use one line python if/else (Danylo)

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Danylo Piliaiev <dpiliaiev@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/13911>