Convert CONFIG_FLASH_CFI_LEGACY to Kconfig

This converts the following to Kconfig:
   CONFIG_FLASH_CFI_LEGACY

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/board/freescale/m5253demo/Kconfig b/board/freescale/m5253demo/Kconfig
index 303d29b..0ecce87 100644
--- a/board/freescale/m5253demo/Kconfig
+++ b/board/freescale/m5253demo/Kconfig
@@ -1,5 +1,9 @@
 if TARGET_M5253DEMO
 
+config FLASH_CFI_LEGACY
+	depends on SYS_FLASH_CFI
+	def_bool y
+
 config SYS_CPU
 	default "mcf52x2"