loader: Don't fall back to nouveau GL without zink

Long term, we don't want to support nouveau gl on new cards. Remove
the fallback so users without zink will get software rendering
instead of nouveau gl.

For now, NOUVEAU_USE_ZINK will still select nouveau gl on cards where
that is possible, but that isn't really supported and will likely be
removed for a lot of cards in the future.

Reviewed-by: Karol Herbst <kherbst@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/36971>

src/loader/loader.c

@@ -143,12 +143,6 @@ nouveau_zink_predicate(int fd, const char *driver)
    if (!drm_fd_is_nouveau(fd))
       return false;
 
-#if !defined(HAVE_NVK) || !defined(HAVE_ZINK)
-   if (!strcmp(driver, "zink"))
-      return false;
-   return true;
-#else
-
    bool prefer_zink = false;
    bool require_zink = false;
 
@@ -197,7 +191,6 @@ nouveau_zink_predicate(int fd, const char *driver)
    if (!use_zink && !strcmp(driver, "nouveau"))
       return true;
    return false;
-#endif
 }