draw: fix tess eval pipeline statistics.

The number of invocations wasn't getting incremented correctly.

Fixes: 202bc38ce9e3 ("draw: collect tessellation invocations statistics")
Reviewed-by: Roland Scheidegger <sroland@vmware.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7597>
(cherry picked from commit ce07c52b825903e698b63bc608d7ddb8cb578cd6)
2 files changed