Convert CONFIG_ATMEL_LEGACY to Kconfig

This converts the following to Kconfig:
   CONFIG_ATMEL_LEGACY

Cc: Eugen Hristev <eugen.hristev@microchip.com>
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/snapper9g20_defconfig b/configs/snapper9g20_defconfig
index 13c4ebe..38c10c8 100644
--- a/configs/snapper9g20_defconfig
+++ b/configs/snapper9g20_defconfig
@@ -6,6 +6,7 @@
 CONFIG_SYS_MALLOC_LEN=0x100000
 CONFIG_TARGET_SNAPPER9260=y
 CONFIG_AT91_GPIO_PULLUP=y
+CONFIG_ATMEL_LEGACY=y
 CONFIG_NR_DRAM_BANKS=1
 CONFIG_ENV_SIZE=0x40000
 CONFIG_ENV_OFFSET=0x80000