imx6: move MXC_GPIO define to mx6_common.h

Define CONFIG_MXC_GPIO and CONFIG_CMD_GPIO by default in mx6_common

Signed-off-by: Peter Robinson <pbrobinson@gmail.com>
diff --git a/include/configs/mx6_common.h b/include/configs/mx6_common.h
index 33c6203..ae25640 100644
--- a/include/configs/mx6_common.h
+++ b/include/configs/mx6_common.h
@@ -52,4 +52,8 @@
 #define CONFIG_INITRD_TAG
 #define CONFIG_REVISION_TAG
 
+/* GPIO */
+#define CONFIG_MXC_GPIO
+#define CONFIG_CMD_GPIO
+
 #endif