siemens/mc_apl1: Select external 8250 UART

The mainboard siemens/mc_apl1 uses an external I/O port for console
output. For this reason we need to activate the 8250 LPC UART.

Change-Id: Ib5616a116aec6135191bdce95f9f9566ce13d6f1
Signed-off-by: Mario Scheithauer <mario.scheithauer@siemens.com>
Reviewed-on: https://review.coreboot.org/19694
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/mainboard/siemens/mc_apl1/Kconfig

@@ -8,6 +8,7 @@ config BOARD_SPECIFIC_OPTIONS
 	select DRIVER_INTEL_I210
 	select USE_SIEMENS_HWILIB
 	select DRIVERS_I2C_RX6110SA
+	select DRIVERS_UART_8250IO
 
 config MAINBOARD_DIR
 	string