sandbox: Only read the state if we have a state file

We should not read this unless requested. Make it conditional on the
option being provided.

Add some debugging to show the state being written.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/sandbox/cpu/start.c b/arch/sandbox/cpu/start.c
index 8582f05..2c8a725 100644
--- a/arch/sandbox/cpu/start.c
+++ b/arch/sandbox/cpu/start.c
@@ -522,9 +522,11 @@
 		state->ram_buf_fname = NULL;
 	}
 
-	ret = sandbox_read_state(state, state->state_fname);
-	if (ret)
-		goto err;
+	if (state->read_state && state->state_fname) {
+		ret = sandbox_read_state(state, state->state_fname);
+		if (ret)
+			goto err;
+	}
 
 	if (state->handle_signals) {
 		ret = os_setup_signal_handlers();