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/model_106cx/Makefile.inc

@@ -1,6 +1,5 @@
 ramstage-y += model_106cx_init.c
 subdirs-y += ../../x86/name
-subdirs-y += ../common
 subdirs-y += ../smm/gen1
 ramstage-$(CONFIG_PARALLEL_MP) += ../model_1067x/mp_init.c