mb/google/glados: disable serial console by default

Glados boards do not have an exposed serial port outside
of the servo interface. Set board Kconfig so that a default
built image with Tianocore payload is bootable and doesn't
hang due to trying to send data over a non-existant serial port.

Test: build/boot google/chell with board defaults

Change-Id: Ifad6f805e66438e2c436d9fa235d9be2ecf69179
Signed-off-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/39863
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Nico Huber <nico.h@gmx.de>

src/mainboard/google/glados/Kconfig

@@ -81,4 +81,8 @@ config UART_FOR_CONSOLE
 	int
 	default 2
 
+config CONSOLE_SERIAL
+	bool
+	default n
+
 endif