dm: rpi: Convert GPIO driver to driver model

Convert the BCM2835 GPIO driver to use driver model, and switch over
Raspberry Pi to use this, since it is the only board.

Signed-off-by: Simon Glass <sjg@chromium.org>
Tested-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Stephen Warren <swarren@wwwdotorg.org>
diff --git a/include/configs/rpi_b.h b/include/configs/rpi_b.h
index 2d69809..d9475e9 100644
--- a/include/configs/rpi_b.h
+++ b/include/configs/rpi_b.h
@@ -31,6 +31,11 @@
  */
 #define CONFIG_MACH_TYPE		MACH_TYPE_BCM2708
 
+/* Enable driver model */
+#define CONFIG_DM
+#define CONFIG_CMD_DM
+#define CONFIG_DM_GPIO
+
 /* Memory layout */
 #define CONFIG_NR_DRAM_BANKS		1
 #define CONFIG_SYS_SDRAM_BASE		0x00000000