sysinfo: Add sysinfo API for accessing data area

Add interface for sysinfo to access a data area from the platform.
This is useful to save/read a memory region of platform-specific
data.

Signed-off-by: Raymond Mao <raymond.mao@linaro.org>
diff --git a/drivers/sysinfo/sysinfo-uclass.c b/drivers/sysinfo/sysinfo-uclass.c
index d77d1e3..3c0cd51 100644
--- a/drivers/sysinfo/sysinfo-uclass.c
+++ b/drivers/sysinfo/sysinfo-uclass.c
@@ -99,6 +99,26 @@
 	return ops->get_str(dev, id, size, val);
 }
 
+int sysinfo_get_data(struct udevice *dev, int id, void **data, size_t *size)
+{
+	struct sysinfo_priv *priv;
+	struct sysinfo_ops *ops;
+
+	if (!dev)
+		return -ENOSYS;
+
+	priv = dev_get_uclass_priv(dev);
+	ops = sysinfo_get_ops(dev);
+
+	if (!priv->detected)
+		return -EPERM;
+
+	if (!ops->get_data)
+		return -ENOSYS;
+
+	return ops->get_data(dev, id, data, size);
+}
+
 UCLASS_DRIVER(sysinfo) = {
 	.id		= UCLASS_SYSINFO,
 	.name		= "sysinfo",