Kconfig: Hide BOARD_ID_MANUAL.

board_id() returns an integer which is platform-specific. 0 for one port
is different from 0 for another port. So there is no default board_id()
and hence enabling it on boards other than urara would cause build failure.
Not enabling it on urara or just setting id to "(none)" as is default results
in board_id() = 0 which means urara and an error message on console.

Change-Id: I94618f36a75e7505984bbec345a31fe0fa9cc867
Signed-off-by: Vladimir Serbinenko <phcoder@gmail.com>
Reviewed-on: http://review.coreboot.org/10379
Tested-by: build bot (Jenkins)
Reviewed-by: Marc Jones <marc@marcjonesconsulting.com>

src/Kconfig

@@ -302,7 +302,7 @@ config BOARD_ID_AUTO
 	  (ie. GPIO) select this configuration option.
 
 config BOARD_ID_MANUAL
-	bool "Add board ID file to CBFS"
+	bool
 	default n
 	depends on !BOARD_ID_AUTO
 	help

src/mainboard/google/urara/Kconfig

@@ -29,6 +29,7 @@ config BOARD_SPECIFIC_OPTIONS
 	select CPU_IMGTEC_PISTACHIO
 	select COMMON_CBFS_SPI_WRAPPER
 	select SPI_FLASH
+	select BOARD_ID_MANUAL
 
 config MAINBOARD_DIR
 	string