x86/kasan: Fix boot with KASAN=y and PROFILE_ANNOTATED_BRANCHES=y

The kernel doesn't boot with both PROFILE_ANNOTATED_BRANCHES=y and KASAN=y
options selected. With branch profiling enabled we end up calling
ftrace_likely_update() before kasan_early_init(). ftrace_likely_update() is
built with KASAN instrumentation, so calling it before kasan has been
initialized leads to crash.

Use DISABLE_BRANCH_PROFILING define to make sure that we don't call
ftrace_likely_update() from early code before kasan_early_init().

Fixes: ef7f0d6a6c ("x86_64: add KASan support")
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: kasan-dev@googlegroups.com
Cc: Alexander Potapenko <glider@google.com>
Cc: stable@vger.kernel.org
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: lkp@01.org
Cc: Dmitry Vyukov <dvyukov@google.com>
Link: http://lkml.kernel.org/r/20170313163337.1704-1-aryabinin@virtuozzo.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/kernel/head64.c

@@ -4,6 +4,7 @@
  *  Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE
  */
 
+#define DISABLE_BRANCH_PROFILING
 #include <linux/init.h>
 #include <linux/linkage.h>
 #include <linux/types.h>

arch/x86/mm/kasan_init_64.c

@@ -1,3 +1,4 @@
+#define DISABLE_BRANCH_PROFILING
 #define pr_fmt(fmt) "kasan: " fmt
 #include <linux/bootmem.h>
 #include <linux/kasan.h>