x86: Add a clock driver for Intel devices

So far we have avoided adding a clock driver for Intel devices. But the
Designware I2C driver needs a different clock (133MHz) on Intel devices
than on others (166MHz). Add a simple driver that provides this
information.

This driver can be expanded later as needed.

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

include/dt-bindings/clock/intel-clock.h

@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * This header provides constants for Intel clocks.
+ *
+ * The constants defined in this header are used in the device tree
+ *
+ * Copyright 2019 Google LLC
+ */
+
+#ifndef _DT_BINDINGS_CLK_INTEL_H
+#define _DT_BINDINGS_CLK_INTEL_H
+
+#define CLK_I2C		1
+
+#endif