sandbox: enable GPIO driver

Enable the new GPIO driver for sandbox.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>

include/configs/sandbox.h

@@ -34,6 +34,10 @@
 
 #define CONFIG_SYS_VSNPRINTF
 
+#define CONFIG_CMD_GPIO
+#define CONFIG_SANDBOX_GPIO
+#define CONFIG_SANDBOX_GPIO_COUNT	20
+
 /*
  * Size of malloc() pool, although we don't actually use this yet.
  */