soc/intel/fsp_broadwell_de: Add vboot support

Enable vboot2 in romstage.

Change-Id: I7f1a1e8538999c5e4e54f3a4aa0cdf6d8a309c4f
Signed-off-by: Philipp Deppenwiese <zaolin.daisuki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/29590
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/intel/fsp_broadwell_de/Kconfig

@@ -29,6 +29,9 @@ config CPU_SPECIFIC_OPTIONS
 	select TSC_MONOTONIC_TIMER
 	select TSC_CONSTANT_RATE
 
+config VBOOT
+	select VBOOT_STARTS_IN_ROMSTAGE
+
 config CBFS_SIZE
 	hex
 	default 0x200000