x86: include optional reference code blob in cbfs

In order to incorporate external blobs into
CBFS besides MRC have a notion of a reference code
blob. By selecting HAVE_REFCODE_BLOB and providing
the file name the refcode blob will be added to
cbfs as a stage file.

BUG=chrome-os-partner:22866
BRANCH=None
TEST=Using this option and other patches able to build,
     boot, and run blob code.

Change-Id: I472604d77f4cb48f286b5a76b25d8b5bfb0c7780
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/174423
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: http://review.coreboot.org/4895
Tested-by: build bot (Jenkins)
Reviewed-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>

src/Kconfig

@@ -429,6 +429,23 @@ config RELOCATABLE_RAMSTAGE
 	 wake. When selecting this option the romstage is responsible for
 	 determing a stack location to use for loading the ramstage.
 
+config HAVE_REFCODE_BLOB
+	depends on ARCH_X86
+	bool "An external reference code blob should be put into cbfs."
+	default n
+	help
+	 The reference code blob will be placed into cbfs.
+
+if HAVE_REFCODE_BLOB
+
+config REFCODE_BLOB_FILE
+	string "Path and filename to reference code blob."
+	default "refcode.elf"
+	help
+	 The path and filename to the file to be added to cbfs.
+
+endif # HAVE_REFCODE_BLOB
+
 config HAVE_ACPI_TABLES
 	bool
 	help

src/arch/x86/Makefile.inc

@@ -136,6 +136,9 @@ endif
 ifeq ($(CONFIG_VBOOT_VERIFY_FIRMWARE),y)
 	$(CBFSTOOL) $@.tmp add-stage -f $(VBOOT_STUB_ELF) -n $(CONFIG_CBFS_PREFIX)/vboot -c $(CBFS_COMPRESS_FLAG)
 endif
+ifeq ($(CONFIG_HAVE_REFCODE_BLOB),y)
+	$(CBFSTOOL) $@.tmp add-stage -f $(CONFIG_REFCODE_BLOB_FILE) -n $(CONFIG_CBFS_PREFIX)/refcode -c $(CBFS_COMPRESS_FLAG)
+endif
 ifeq ($(CONFIG_PXE_ROM),y)
 	$(CBFSTOOL) $@.tmp add -f $(CONFIG_PXE_ROM_FILE) -n pci$(CONFIG_PXE_ROM_ID).rom -t raw
 endif