usbdebug: Add option to disable console for romstage

If there is trouble setting up usbdebug, it may be useful to delay
usbdebug init to run in ramstage.

Change-Id: I31de5a06d3f9ce19f71c422cce0c8cb0fd50f396
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: http://review.coreboot.org/4488
Tested-by: build bot (Jenkins)
Reviewed-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Aaron Durbin <adurbin@google.com>

src/console/Kconfig

@@ -173,13 +173,19 @@ config USBDEBUG
 
 	  If unsure, say N.
 
-config USBDEBUG_IN_ROMSTAGE
-	bool
-	default y if USBDEBUG && EARLY_CBMEM_INIT && EARLY_CONSOLE
-	default n
-
 if USBDEBUG
 
+config USBDEBUG_IN_ROMSTAGE
+	bool "Enable early (pre-RAM) usbdebug console output."
+	default y
+	depends on EARLY_CBMEM_INIT && EARLY_CONSOLE
+	help
+	   Configuring USB controllers in system-agent binary may cause
+	   problems to usbdebug. Disabling this option delays usbdebug to
+	   be setup on entry to ramstage.
+
+	   If unsure, say Y.
+
 config USBDEBUG_HCD_INDEX
 	int
 	default 0