timer: sandbox: work without device tree

A default invocation of sandbox U-Boot apparently uses no device tree,
which means that no timer is registers, which in turn means that the
sleep shell command hangs.

Fix the sandbox timer code to register a device when there's no DT, just
like e.g. the sandbox reset driver does. When there's no DT, the DM uclass
can't initialize clock_rate from DT, so set a default value in the
timer code instead.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Acked-by: Simon Glass <sjg@chromium.org>

drivers/timer/sandbox_timer.c

@@ -27,6 +27,11 @@ static int sandbox_timer_get_count(struct udevice *dev, u64 *count)
 
 static int sandbox_timer_probe(struct udevice *dev)
 {
+	struct timer_dev_priv *uc_priv = dev_get_uclass_priv(dev);
+
+	if (!uc_priv->clock_rate)
+		uc_priv->clock_rate = 1000000;
+
 	return 0;
 }
 
@@ -47,3 +52,8 @@ U_BOOT_DRIVER(sandbox_timer) = {
 	.ops	= &sandbox_timer_ops,
 	.flags = DM_FLAG_PRE_RELOC,
 };
+
+/* This is here in case we don't have a device tree */
+U_BOOT_DEVICE(sandbox_timer_non_fdt) = {
+	.name = "sandbox_timer",
+};