Revert "x86/speculation: Enable cross-hyperthread spectre v2 STIBP mitigation"

Revert "x86/speculation: Enable cross-hyperthread spectre v2 STIBP mitigation"

This reverts commit 233b9d7df0e114c7e7c3674559fb0fc41ada3e8f which is
commit 53c613fe6349994f023245519265999eed75957f upstream.

It's not ready for the stable trees as there are major slowdowns
involved with this patch.

Reported-by: Jiri Kosina <jkosina@suse.cz>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc:  "WoodhouseDavid" <dwmw@amazon.co.uk>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc:  "SchauflerCasey" <casey.schaufler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>