drivers: i2c: mentor: move platform code into header files

At the moment we have two I2C stub drivers (for the Allwinner and the
Marvell platform), which #include the actual .c driver file.
Change this into the more usual design, by renaming and moving the stub
drivers into platform specific header files and including these from the
actual driver file. The platform specific include directories make sure
the driver picks up the right header automatically.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
diff --git a/plat/allwinner/common/include/mentor_i2c_plat.h b/plat/allwinner/common/include/mentor_i2c_plat.h
new file mode 100644
index 0000000..f547f9a
--- /dev/null
+++ b/plat/allwinner/common/include/mentor_i2c_plat.h
@@ -0,0 +1,28 @@
+/*
+ * Copyright (C) 2018 Icenowy Zheng <icenowy@aosc.io>
+ *
+ * SPDX-License-Identifier:     BSD-3-Clause
+ * https://spdx.org/licenses
+ */
+/* This driver provides I2C support for Allwinner sunXi SoCs */
+
+#ifndef SUNXI_I2C_H
+#define SUNXI_I2C_H
+
+#define CONFIG_SYS_TCLK			24000000
+#define CONFIG_SYS_I2C_SPEED		100000
+#define CONFIG_SYS_I2C_SLAVE		0
+
+#define I2C_INTERRUPT_CLEAR_INVERTED
+
+struct  mentor_i2c_regs {
+	uint32_t slave_address;
+	uint32_t xtnd_slave_addr;
+	uint32_t data;
+	uint32_t control;
+	uint32_t status;
+	uint32_t baudrate;
+	uint32_t soft_reset;
+};
+
+#endif