soc/samsung/exynos5420: Disable BOOTBLOCK_CONSOLE

Add a new Kconfig NO_BOOTBLOCK_CONSOLE to disable the BOOTBLOCK_CONSOLE
option completely. The commit message of fbb11cf (ARM: Separate the
early console (romstage) from the bootblock console.) states that it
doesn't work before romstage on Exynos 5420.

Change-Id: I9b56a52f2555b5233300f27031a9ef50e7ab7cea
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/30926
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>

src/console/Kconfig

@@ -1,8 +1,11 @@
 menu "Console"
 
+config NO_BOOTBLOCK_CONSOLE
+	bool
+
 config BOOTBLOCK_CONSOLE
 	bool "Enable early (bootblock) console output."
-	depends on C_ENVIRONMENT_BOOTBLOCK
+	depends on C_ENVIRONMENT_BOOTBLOCK && !NO_BOOTBLOCK_CONSOLE
 	default y
 	help
 	  Use console during the bootblock if supported

src/soc/samsung/exynos5420/Kconfig

@@ -7,6 +7,7 @@ config CPU_SAMSUNG_EXYNOS5420
 	select GENERIC_UDELAY
 	select HAVE_UART_SPECIAL
 	select RELOCATABLE_MODULES
+	select NO_BOOTBLOCK_CONSOLE
 	bool
 	default n