ARM: Add mediatek SoC UART support in defconfig

Add mediatek SoC UART support in multi_v7_defconfig
Signed-off-by: NEddie Huang <eddie.huang@mediatek.com>
Signed-off-by: NMatthias Brugger <matthias.bgg@gmail.com>

arch/arm/configs/multi_v7_defconfig

@@ -195,6 +195,7 @@ CONFIG_SERIO_AMBAKMI=y
 CONFIG_SERIAL_8250=y
 CONFIG_SERIAL_8250_CONSOLE=y
 CONFIG_SERIAL_8250_DW=y
+CONFIG_SERIAL_8250_MT6577=y
 CONFIG_SERIAL_AMBA_PL011=y
 CONFIG_SERIAL_AMBA_PL011_CONSOLE=y
 CONFIG_SERIAL_MESON=y