Convert CONFIG_MCFUART to Kconfig

This converts the following to Kconfig:
	CONFIG_MCFUART

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/M5253DEMO_defconfig b/configs/M5253DEMO_defconfig
index e8dca52..423e2f7 100644
--- a/configs/M5253DEMO_defconfig
+++ b/configs/M5253DEMO_defconfig
@@ -26,3 +26,4 @@
 CONFIG_SYS_I2C_SLAVE=0x7F
 CONFIG_SYS_I2C_SPEED=80000
 CONFIG_MTD_NOR_FLASH=y
+CONFIG_MCFUART=y