egl/surfaceless: Enable RGBA configs

Doing this is harmless since we operate on an allowlist of pipe_configs
anyway.

Signed-off-by: Daniel Stone <daniels@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/29837>

src/egl/drivers/dri2/platform_surfaceless.c

@@ -190,6 +190,8 @@ surfaceless_get_capability(void *loaderPrivate, enum dri_loader_cap cap)
    switch (cap) {
    case DRI_LOADER_CAP_FP16:
       return 1;
+   case DRI_LOADER_CAP_RGBA_ORDERING:
+      return 1;
    default:
       return 0;
    }