cbfs/vboot: remove firmware component support

The Chrome OS verified boot path supported multiple CBFS
instances in the boot media as well as stand-alone assets
sitting in each vboot RW slot. Remove the support for the
stand-alone assets and always use CBFS accesses as the
way to retrieve data.

This is implemented by adding a cbfs_locator object which
is queried for locating the current CBFS. Additionally, it
is also signalled prior to when a program is about to be
loaded by coreboot for the subsequent stage/payload. This
provides the same opportunity as previous for vboot to
hook in and perform its logic.

BUG=chromium:445938
BRANCH=None
TEST=Built and ran on glados.
CQ-DEPEND=CL:307121,CL:31691,CL:31690

Change-Id: I6a3a15feb6edd355d6ec252c36b6f7885b383099
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/12689
Tested-by: build bot (Jenkins)
Tested-by: Raptor Engineering Automated Test Stand <noreply@raptorengineeringinc.com>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

src/vendorcode/google/chromeos/Kconfig

@@ -28,6 +28,7 @@ config CHROMEOS
 	select ELOG if SPI_FLASH
 	select COLLECT_TIMESTAMPS
 	select VBOOT_VERIFY_FIRMWARE
+	select MULTIPLE_CBFS_INSTANCES
 	help
 	  Enable ChromeOS specific features like the GPIO sub table in
 	  the coreboot table. NOTE: Enabling this option on an unsupported