cpu/intel/sandybridge: Put stage cache into TSEG

TSEG is not accessible in ring 0 after it is locked in ramstage, in
contrast with cbmem which remains accessible. Assuming SMM does not
touch the cache this is a good region to cache stages.

The code is mostly copied from src/cpu/intel/haswell.

TESTED on Thinkpad X220: on a cold boot the stage cache gets created
and on S3 the cached ramstage gets properly used.

Change-Id: Ifd8f939416b1712f6e5c74f544a5828745f8c2f2
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/23592
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
diff --git a/src/cpu/intel/model_206ax/Makefile.inc b/src/cpu/intel/model_206ax/Makefile.inc
index 7516e9d..1e04554 100644
--- a/src/cpu/intel/model_206ax/Makefile.inc
+++ b/src/cpu/intel/model_206ax/Makefile.inc
@@ -11,6 +11,9 @@
 
 smm-$(CONFIG_HAVE_SMI_HANDLER) += finalize.c
 
+romstage-$(CONFIG_CACHE_RELOCATED_RAMSTAGE_OUTSIDE_CBMEM) += stage_cache.c
+ramstage-$(CONFIG_CACHE_RELOCATED_RAMSTAGE_OUTSIDE_CBMEM) += stage_cache.c
+
 cpu_microcode_bins += 3rdparty/blobs/cpu/intel/model_206ax/microcode.bin
 cpu_microcode_bins += 3rdparty/blobs/cpu/intel/model_306ax/microcode.bin