llvmpipe/cs: update compute counters not fragment shader.

This was updating the wrong counters.

Reviewed-by: Eric Engestrom <eric@engestrom.ch>
Fixes: a6f6ca37c82bb6810971 ("llvmpipe: add initial shader create/bind/destroy variants framework.")
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6339>