cpu/intel/hyperthreading: Build only for selected models

Implements intel_sibling_init() that is mostly superseded.

Change-Id: I4956493d8c0c6b922343e060d2d2bd0ec20f5bb6
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/55201
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/cpu/intel/socket_441/Makefile.inc

@@ -4,7 +4,6 @@ subdirs-y += ../../x86/mtrr
 subdirs-y += ../../x86/lapic
 subdirs-y += ../../x86/cache
 subdirs-y += ../microcode
-subdirs-y += ../hyperthreading
 subdirs-y += ../speedstep
 
 bootblock-y += ../car/p4-netburst/cache_as_ram.S