dm: i2c: Add I2C emulation driver for sandbox

In order to test I2C we need some sort of emulation interface. Add hooks
to allow a driver to emulate an I2C device for sandbox.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Heiko Schocher <hs@denx.de>
Reviewed-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
diff --git a/drivers/i2c/i2c-emul-uclass.c b/drivers/i2c/i2c-emul-uclass.c
new file mode 100644
index 0000000..aa89f95
--- /dev/null
+++ b/drivers/i2c/i2c-emul-uclass.c
@@ -0,0 +1,14 @@
+/*
+ * Copyright (c) 2014 Google, Inc
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <i2c.h>
+
+UCLASS_DRIVER(i2c_emul) = {
+	.id		= UCLASS_I2C_EMUL,
+	.name		= "i2c_emul",
+};