r600: don't emit atomic save if we have no atomic counters.

Otherwise we end up emitting the fence.

Tested-By: Gert Wollny <gw.fossdev@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

src/gallium/drivers/r600/evergreen_state.c

@@ -4221,6 +4221,9 @@ void evergreen_emit_atomic_buffer_save(struct r600_context *rctx,
 	unsigned reloc;
 
 	mask = *atomic_used_mask_p;
+	if (!mask)
+		return;
+
 	while (mask) {
 		unsigned atomic_index = u_bit_scan(&mask);
 		struct r600_shader_atomic *atomic = &combined_atomics[atomic_index];