mb/google/rambi: Disable console output by default

Disable SoC serial output by default, since no production devices
have this exposed, but leave it as a user option so it can be selected
as needed (eg, for use with a Google debug servo).

Same change as made for google/cyan in CB:39872

Change-Id: Id6b2c28658aca03d8c5042d719a0f6f504c29288
Signed-off-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/39997
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

src/mainboard/google/rambi/Kconfig

@@ -4,7 +4,7 @@ config BOARD_GOOGLE_BASEBOARD_RAMBI
 	select SOC_INTEL_BAYTRAIL
 	select EC_GOOGLE_CHROMEEC
 	select EC_GOOGLE_CHROMEEC_LPC
-	select ENABLE_BUILTIN_COM1
+	select ENABLE_BUILTIN_COM1 if CONSOLE_SERIAL
 	select BOARD_ROMSIZE_KB_8192
 	select HAVE_ACPI_TABLES
 	select HAVE_OPTION_TABLE
@@ -76,4 +76,7 @@ config MAINBOARD_SMBIOS_MANUFACTURER
 	string
 	default "GOOGLE"
 
+config CONSOLE_SERIAL
+	default n
+
 endif # BOARD_GOOGLE_BASEBOARD_RAMBI