arch/x86: Enable ebda library for romstage and postcar

This patch provides a kconfig option as EARLY_EBDA_INIT to
ensures user can make use of EBDA library even during early
boot stages like romstage, postcar.

Change-Id: I603800a531f56b6ebd460d5951c35a645fbfe492
Signed-off-by: Subrata Banik <subrata.banik@intel.com>
Reviewed-on: https://review.coreboot.org/21388
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Sumeet R Pawnikar <sumeet.r.pawnikar@intel.com>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/arch/x86/Makefile.inc

@@ -209,6 +209,7 @@ romstage-y += boot.c
 romstage-y += cbmem.c
 romstage-y += cbfs_and_run.c
 romstage-$(CONFIG_ARCH_RAMSTAGE_X86_32) += cpu_common.c
+romstage-$(CONFIG_EARLY_EBDA_INIT) += ebda.c
 romstage-y += memcpy.c
 romstage-y += memmove.c
 romstage-y += memset.c
@@ -283,6 +284,7 @@ postcar-y += boot.c
 postcar-y += cbfs_and_run.c
 postcar-y += cbmem.c
 postcar-y += cpu_common.c
+postcar-$(CONFIG_EARLY_EBDA_INIT) += ebda.c
 postcar-y += exit_car.S
 postcar-y += memcpy.c
 postcar-y += memmove.c