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/taurus_defconfig b/configs/taurus_defconfig
index 0b25c3d..e7b6617 100644
--- a/configs/taurus_defconfig
+++ b/configs/taurus_defconfig
@@ -14,6 +14,7 @@
 CONFIG_SYS_MALLOC_F_LEN=0x2000
 CONFIG_TARGET_TAURUS=y
 CONFIG_AT91_GPIO_PULLUP=y
+CONFIG_ATMEL_LEGACY=y
 CONFIG_BOARD_TAURUS=y
 CONFIG_SPL_GPIO=y
 CONFIG_SPL_LIBCOMMON_SUPPORT=y