at91: enable USB ethernet for taskit stamp9g20

enabling CONFIG_MACB makes other locations in the stamp config file
enable network related commands (actually prevents disabling them)

enable USB ethernet support by activating generic support as well as
Asix and Moschip ethernet adapters

Signed-off-by: Gerhard Sittig <gsi@denx.de>
Acked-by: Andreas Bießman <andreas.devel@googlemail.com>

include/configs/stamp9g20.h

@@ -140,7 +140,10 @@
  * can enable it here if your baseboard features ethernet.
  */
 
-/* #define CONFIG_MACB */
+#define CONFIG_MACB
+#define CONFIG_USB_HOST_ETHER
+#define CONFIG_USB_ETHER_ASIX
+#define CONFIG_USB_ETHER_MCS7830
 
 #ifdef CONFIG_MACB
 # define CONFIG_RMII			/* use reduced MII inteface */