dm: exynos: Move serial to driver model

Change the Exynos serial driver to work with driver model and switch over
all relevant boards to use it.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/configs/s5p_goni.h b/include/configs/s5p_goni.h
index 76b0503..3633a35 100644
--- a/include/configs/s5p_goni.h
+++ b/include/configs/s5p_goni.h
@@ -292,5 +292,6 @@
 #define CONFIG_DM
 #define CONFIG_CMD_DM
 #define CONFIG_DM_GPIO
+#define CONFIG_DM_SERIAL
 
 #endif	/* __CONFIG_H */