intel/perf: report query split for mdapi

intel/perf: report query split for mdapi

Also forgotten in the initial implementation.

v2: Report begin timestamp scaled by the timestamp frequency (Windows
    behavior)

v3: Rename split to disjoint to match GL terminology (Tapani)

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: <mesa-stable@lists.freedesktop.org>
Acked-by: Tapani Pälli <tapani.palli@intel.com>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3112>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3112>