gallium: Fix leak of the merged driconf options.

Fixes: 8a05d6ffc65d ("driconf: Make the driver's declarations be structs instead of XML.")
Reviewed-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7695>
(cherry picked from commit 0626e3a950d5dbe5d86244670b54b67a2af6014c)
2 files changed