Convert CONFIG_AT91_LED to Kconfig

This converts the following to Kconfig:
   CONFIG_AT91_LED

Cc: Eugen Hristev <eugen.hristev@microchip.com>
Signed-off-by: NTom Rini <trini@konsulko.com>

board/siemens/corvus/Kconfig

 if TARGET_CORVUS
 
+config AT91_LED
+	def_bool y
+
 config SYS_BOARD
 	default "corvus"
 

include/configs/corvus.h

@@ -32,7 +32,6 @@
 #define CONFIG_USART_ID			ATMEL_ID_SYS
 
 /* LED */
-#define CONFIG_AT91_LED
 #define CONFIG_RED_LED		AT91_PIN_PD31	/* this is the user1 led */
 #define CONFIG_GREEN_LED	AT91_PIN_PD0	/* this is the user2 led */