sysreset: Add get_status method

It's useful to have the reset status of the SoC printed out during reset
(e.g. to learn whether the reset was caused by software or a watchdog).

As a first step to implement this, add a get_status method to the
sysreset class, which enables the caller to get printable information
about the reset status (akin to get_desc in the CPU uclass).

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Mario Six <mario.six@gdsys.cc>
diff --git a/drivers/sysreset/sysreset-uclass.c b/drivers/sysreset/sysreset-uclass.c
index b918365..06ef0ed 100644
--- a/drivers/sysreset/sysreset-uclass.c
+++ b/drivers/sysreset/sysreset-uclass.c
@@ -24,6 +24,16 @@
 	return ops->request(dev, type);
 }
 
+int sysreset_get_status(struct udevice *dev, char *buf, int size)
+{
+	struct sysreset_ops *ops = sysreset_get_ops(dev);
+
+	if (!ops->get_status)
+		return -ENOSYS;
+
+	return ops->get_status(dev, buf, size);
+}
+
 int sysreset_walk(enum sysreset_t type)
 {
 	struct udevice *dev;