Revert "x86, bts: reenable ptrace branch trace support"

This reverts commit 7e0bfad2.

A late objection to the ABI has arrived:

   http://lkml.org/lkml/2009/6/10/253

Keep the ABI disabled out of caution, to not create premature
user-space expectations.

While the hw-branch-tracing variant uses and tests the BTS code.

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Markus Metzger <markus.t.metzger@intel.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

arch/x86/Kconfig.cpu

@@ -506,6 +506,7 @@ config X86_PTRACE_BTS
 	bool "Branch Trace Store"
 	default y
 	depends on X86_DEBUGCTLMSR
+	depends on BROKEN
 	---help---
 	  This adds a ptrace interface to the hardware's branch trace store.