I cut-n-paste this badly from the non-indexed, and used the wrong
struct.
Fixes a bunch of multi-draw CTS
Fixes: cc8f7dbf2a ("lavapipe: fix multi-draw regression in shader parameters test")
Reviewed-By: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11899>