dm: Add a power sequencing uclass

Some devices need special sequences to be used when starting up. Add a
uclass for this. Drivers can be added to provide specific features as
needed.

Signed-off-by: Simon Glass <sjg@chromium.org>

drivers/misc/pwrseq-uclass.c

@@ -0,0 +1,24 @@
+/*
+ * Copyright (c) 2015 Google, Inc
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <pwrseq.h>
+
+int pwrseq_set_power(struct udevice *dev, bool enable)
+{
+	struct pwrseq_ops *ops = pwrseq_get_ops(dev);
+
+	if (!ops->set_power)
+		return -ENOSYS;
+
+	return ops->set_power(dev, enable);
+}
+
+UCLASS_DRIVER(pwrseq) = {
+	.id		= UCLASS_PWRSEQ,
+	.name		= "pwrseq",
+};