arch/x86: Link walkcbfs.S instead of including it

Link walkfcbfs.S in the C_ENVIRONMENT_BOOTBLOCK case and also in the
romstage.

This is useful for cbfs access in pre-CAR environments.

Change-Id: I9a17cdf01c7cbc3c9ac45ed1f075731f3e32f64b
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/30681
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>

src/arch/x86/Makefile.inc

@@ -122,6 +122,8 @@ else
 $(eval $(call early_x86_stage,bootblock,elf64-x86-64))
 endif
 
+bootblock-y += walkcbfs.S
+
 else # !C_ENVIRONMENT_BOOTBLOCK
 
 # x86-specific linker flags
@@ -233,6 +235,7 @@ romstage-y += memset.c
 romstage-$(CONFIG_X86_TOP4G_BOOTMEDIA_MAP) += mmap_boot.c
 romstage-y += postcar_loader.c
 romstage-$(CONFIG_COLLECT_TIMESTAMPS_TSC) += timestamp.c
+romstage-y += walkcbfs.S
 
 romstage-srcs += $(wildcard $(src)/mainboard/$(MAINBOARDDIR)/romstage.c)
 romstage-libs ?=