turnip: Don't link the WSI code if we don't have a WSI extension.

I don't like the TU_HAS_SURFACE duplication, but this is a step to having
a non-libdrm-dependent turnip on Android with KGSL (which doesn't have
drm for rendering).

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6821>
2 files changed