mainboards: Add CHROMEOS_VBNV_* where appropriate

For boards with MAINBOARD_HAS_CHROMEOS, we should also
state what kind of storage is available for vboot's
non-volatile data.

The flags are taken from the chromium repository and
have no effect with CHROMEOS disabled.

Change-Id: I1747ad26c8c7f6d4076740ec2800dbd52c5d6b3d
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Reviewed-on: http://review.coreboot.org/9952
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/mainboard/google/nyan/Kconfig

@@ -33,6 +33,7 @@ config BOARD_SPECIFIC_OPTIONS # dummy
 	select SPI_FLASH
 	select SPI_FLASH_FAST_READ_DUAL_OUTPUT_3B
 	select VIRTUAL_DEV_SWITCH
+	select CHROMEOS_VBNV_EC
 
 config MAINBOARD_DIR
 	string