x86: Implement functions for writing coreboot table

To prepare generating coreboot table from U-Boot, implement functions
to handle the writing.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
index 4fc1936..6e0234a 100644
--- a/arch/x86/lib/Makefile
+++ b/arch/x86/lib/Makefile
@@ -10,6 +10,7 @@
 obj-y += bios_interrupts.o
 obj-$(CONFIG_CMD_BOOTM) += bootm.o
 obj-y	+= cmd_boot.o
+obj-y	+= coreboot_table.o
 obj-$(CONFIG_EFI) += efi/
 obj-y	+= e820.o
 obj-y	+= gcc.o