security/vboot: Allow files to go into only RW-A or RW-B region

The AMD firmware package created by amdfwtool contains pointers to the
various binaries and settings.  This means that we need different copies
of the package in each region.
This change allows for the different files in each of the 3 vboot
regions.

BUG=b:158124527
TEST=Build trembyle; see the correct versions of the files getting
built into the RW-A & RW-B regions.

Signed-off-by: Martin Roth <martin@coreboot.org>
Change-Id: I45ff69dbc2266a67e05597bbe721fbf95cf41777
Reviewed-on: https://review.coreboot.org/c/coreboot/+/42822
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Raul Rangel <rrangel@chromium.org>

src/security/vboot/Kconfig

@@ -218,6 +218,22 @@ config RW_REGION_ONLY
 	  Add a space delimited list of filenames that should only be in the
 	  RW sections.
 
+config RWA_REGION_ONLY
+	string
+	default ""
+	depends on VBOOT_SLOTS_RW_AB
+	help
+	  Add a space-delimited list of filenames that should only be in the
+	  RW-A section.
+
+config RWB_REGION_ONLY
+	string
+	default ""
+	depends on VBOOT_SLOTS_RW_AB
+	help
+	  Add a space-delimited list of filenames that should only be in the
+	  RW-B section.
+
 config VBOOT_ENABLE_CBFS_FALLBACK
 	bool
 	default n