vboot: Select SoC-specific configuration for all Chrome OS boards

Some Chrome OS boards previously didn't have a hardcoded vboot
configuration (e.g. STARTS_IN_BOOTBLOCK/_ROMSTAGE, SEPARATE_VERSTAGE,
etc.) selected from their SoC and mainboard Kconfig files, and instead
relied on the Chrome OS build system to pass in those options
separately. Since there is usually only one "best" vboot configuration
for a certain board and there is often board or SoC code specifically
written with that configuration in mind (e.g. memlayout), these options
should not be adjustable in menuconfig and instead always get selected
by board and SoC Makefiles (as opposed to some external build system).

(Removing MAINBOARD_HAS_CHROMEOS from Urara because vboot support for
Pistachio/MIPS was never finished. Trying to enable even post-romstage
vboot leads to weird compiler errors that I don't want to track down
now. Let's stop pretending this board has working Chrome OS support
because it never did.)

Change-Id: Ibddf413568630f2e5d6e286b9eca6378d7170104
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://review.coreboot.org/19022
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/soc/intel/baytrail/Kconfig

@@ -39,6 +39,9 @@ config CPU_SPECIFIC_OPTIONS
 	select HAVE_INTEL_FIRMWARE
 	select HAVE_SPI_CONSOLE_SUPPORT
 
+config VBOOT
+	select VBOOT_STARTS_IN_ROMSTAGE
+
 config BOOTBLOCK_CPU_INIT
 	string
 	default "soc/intel/baytrail/bootblock/bootblock.c"