x86: X86_HT always enable on X86_64 SMP

X86_HT is used for hyperthreading or multicore on 32-bit.
The X86_HT on 64-bit is different from 32-bit, it means hyperthreading only.
And X86_HT is not used on 64-bit except from cpu/initel_cacheinfo.c.

Unify X86_HT for hyperthreading or multicore.
Turn X86_HT on when X86_64 and SMP are enabled.

Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>