radeonsi: prevent u_blitter recursion in si_update_ps_colorbuf0_slot

When u_blitter calls util_blitter_restore_fragment_states we may
end up in si_update_ps_colorbuf0_slot.
This commit makes sure we don't call u_blitter from there.

Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/6921
Cc: mesa-stable
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/17981>

src/gallium/drivers/radeonsi/si_descriptors.c

@@ -947,7 +947,7 @@ void si_update_ps_colorbuf0_slot(struct si_context *sctx)
    struct pipe_surface *surf = NULL;
 
    /* si_texture_disable_dcc can get us here again. */
-   if (sctx->in_update_ps_colorbuf0_slot) {
+   if (sctx->in_update_ps_colorbuf0_slot || sctx->blitter_running) {
       assert(!sctx->ps_uses_fbfetch || sctx->framebuffer.state.cbufs[0]);
       return;
    }