arch/x86: Declare GDT symbols and move_gdt()

We relocate GDT to CBMEM, this can be done late in ramstage.
Note: We currently do this for BSP CPU only.

Change-Id: I626faaf22f846433f25ca2253d6a2a5230f50b6b
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: http://review.coreboot.org/7858
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Tested-by: build bot (Jenkins)
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>

src/arch/x86/boot/tables.c

@@ -21,6 +21,7 @@
 
 #include <console/console.h>
 #include <cpu/cpu.h>
+#include <cpu/x86/gdt.h>
 #include <boot/tables.h>
 #include <boot/coreboot_tables.h>
 #include <arch/pirq_routing.h>
@@ -28,7 +29,6 @@
 #include <arch/acpi.h>
 #include <string.h>
 #include <cbmem.h>
-#include <lib.h>
 #include <smbios.h>