dm: Move CONFIG_I2C_COMPAT to Kconfig

Make this option available in Kconfig and clean up the board that uses it.
Note there is also an entry in exynos5-common.h but this affects multiple
boards and should be dropped as part of the Samsung I2C migration to
driver model.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/configs/exynos5-common.h b/include/configs/exynos5-common.h
index 0ba39a2..3ab8d55 100644
--- a/include/configs/exynos5-common.h
+++ b/include/configs/exynos5-common.h
@@ -126,6 +126,8 @@
 #define SPI_FLASH_UBOOT_POS	(CONFIG_SEC_FW_SIZE + CONFIG_BL1_SIZE)
 
 /* I2C */
+
+/* TODO(sjg@chromium.org): Move these two options to Kconfig */
 #define CONFIG_DM_I2C
 #define CONFIG_DM_I2C_COMPAT
 #define CONFIG_CMD_I2C