Convert CONFIG_AT91SAM9G10EK et al to Kconfig

This converts the following to Kconfig:
   CONFIG_AT91SAM9G10EK
   CONFIG_AT91SAM9261EK
   CONFIG_AT91SAM9G10

Cc: Eugen Hristev <eugen.hristev@microchip.com>
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/board/atmel/at91sam9261ek/Kconfig b/board/atmel/at91sam9261ek/Kconfig
index 2971b3c..6133efe 100644
--- a/board/atmel/at91sam9261ek/Kconfig
+++ b/board/atmel/at91sam9261ek/Kconfig
@@ -9,4 +9,18 @@
 config SYS_CONFIG_NAME
 	default "at91sam9261ek"
 
+choice
+	prompt "Evaluation board"
+
+config AT91SAM9G10EK
+	bool "Atmel AT91SAM9G10 EK"
+
+config AT91SAM9261EK
+	bool "Atmel AT91SAM9261 EK"
+
+config AT91SAM9G10
+	bool "Atmel AT91SAM9G10 EK"
+
+endchoice
+
 endif