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>

src/cpu/intel/common/Makefile.inc

@@ -1,4 +1,5 @@
-ramstage-y += common_init.c
+ramstage-$(CONFIG_CPU_INTEL_COMMON) += common_init.c
+ramstage-$(CONFIG_CPU_INTEL_COMMON_HYPERTHREADING) += hyperthreading.c
 
 ifeq ($(CONFIG_CPU_INTEL_COMMON_TIMEBASE),y)
 bootblock-y += fsb.c