sandbox: Drop message about writing sandbox state

This happens every time sandbox moves to the next phase so is not very
interesting. Display the message only when debugging.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>

arch/sandbox/cpu/state.c

@@ -470,7 +470,7 @@ int state_uninit(void)
 	int err;
 
 	if (state->write_ram_buf || state->write_state)
-		log_info("Writing sandbox state\n");
+		log_debug("Writing sandbox state\n");
 	state = &main_state;
 
 	/* Finish the bloblist, so that it is correct before writing memory */