dm: exynos: gpio: Convert to driver model

Convert the exynos GPIO driver to driver model. This implements the generic
GPIO interface but not the extra Exynos-specific functions.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/configs/exynos-common.h b/include/configs/exynos-common.h
index 371f32d..4a4b22b 100644
--- a/include/configs/exynos-common.h
+++ b/include/configs/exynos-common.h
@@ -17,6 +17,10 @@
 #include <linux/sizes.h>
 
 #define CONFIG_SYS_GENERIC_BOARD
+#define CONFIG_DM
+#define CONFIG_CMD_DM
+#define CONFIG_DM_GPIO
+
 #define CONFIG_ARCH_CPU_INIT
 #define CONFIG_DISPLAY_CPUINFO
 #define CONFIG_DISPLAY_BOARDINFO