chromeos/vboot: provide support for x86 memory init verification

For x86 systems which resume through the reset vector one needs to
ensure the the RW slot taken at resume time matches the one at
boot time. The reason is that any assets pulled out of the boot
media need to match how the platform previously booted. To do
that one needs obtain the hash digest of the chosen slot, and it
needs to be saved in a secure place on the normal boot path. On
resume one needs to retrieve the hash digest back to compare it
with the chosen slot. If they don't match resuming won't be
possible.

BUG=chrome-os-partner:46049
BRANCH=glados
TEST=Suspended and resumed on chell. Also, tested with an EC build
     which returns a bad hash to ensure that is properly caught.
CQ-DEPEND=CL:323460

Change-Id: I90ce26813b67f46913aa4026b42d9490a564bb6c
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: 01a42c0ecfc6d60d1d2e5e36a86781d91d5c47a9
Original-Change-Id: I6c6bdce7e06712bc06cc620a3d7a6a6250c59c95
Original-Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/323500
Original-Reviewed-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Reviewed-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: https://review.coreboot.org/13574
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

src/Kconfig

@@ -503,6 +503,15 @@ config HAVE_ACPI_RESUME
 	bool
 	default n
 
+config RESUME_PATH_SAME_AS_BOOT
+	bool
+	default y if ARCH_X86
+	depends on HAVE_ACPI_RESUME
+	help
+	  This option indicates that when a system resumes it takes the
+	  same path as a regular boot. e.g. an x86 system runs from the
+	  reset vector at 0xfffffff0 on both resume and warm/cold boot.
+
 config HAVE_HARD_RESET
 	bool
 	default n