nir: Include num_ubos in the printed shader (if nonzero).

I keep wanting this number for debugging shaders.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4858>
diff --git a/src/compiler/nir/nir_print.c b/src/compiler/nir/nir_print.c
index 6fc8fc9..e9b6b10 100644
--- a/src/compiler/nir/nir_print.c
+++ b/src/compiler/nir/nir_print.c
@@ -1496,6 +1496,8 @@
    fprintf(fp, "inputs: %u\n", shader->num_inputs);
    fprintf(fp, "outputs: %u\n", shader->num_outputs);
    fprintf(fp, "uniforms: %u\n", shader->num_uniforms);
+   if (shader->info.num_ubos)
+      fprintf(fp, "ubos: %u\n", shader->info.num_ubos);
    fprintf(fp, "shared: %u\n", shader->num_shared);
    if (shader->scratch_size)
       fprintf(fp, "scratch: %u\n", shader->scratch_size);