cpu/intel/common: Move intel_ht_sibling() to common folder

Make intel_ht_sibling() available on all platforms.

Will be used in MP init to only write "Core" MSRs from one thread
on HyperThreading enabled platforms, to prevent race conditions and
resulting #GP if MSRs are written twice or are already locked.

Change-Id: I5d000b34ba4c6536dc866fbaf106b78e905e3e35
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/35619
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
diff --git a/src/cpu/intel/Makefile.inc b/src/cpu/intel/Makefile.inc
index 3f89740..484e241 100644
--- a/src/cpu/intel/Makefile.inc
+++ b/src/cpu/intel/Makefile.inc
@@ -16,3 +16,5 @@
 subdirs-$(CONFIG_NORTHBRIDGE_INTEL_FSP_RANGELEY) += fsp_model_406dx
 subdirs-$(CONFIG_CPU_INTEL_SLOT_1) += slot_1
 subdirs-$(CONFIG_CPU_INTEL_SOCKET_LGA775) += socket_LGA775
+
+subdirs-y += common