arch/x86: Relocate GDT in verstage, romstage, and postcar

In each stage keep GDT in the code region. This accommodates
platforms, such as glk, that are executing out of CAR. The
gdt is small and loading it is trivial so just do it unconditionally
instead of introducing another Kconfig.

BUG=b:78656686

Change-Id: I01ded6e9b358b23e04d92bef5263bfe8c2a5ec5a
Signed-off-by: Hannah Williams <hannah.williams@intel.com>
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/25895
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Justin TerAvest <teravest@chromium.org>
5 files changed