x86/tsc: Remove the unused check_tsc_disabled()

check_tsc_disabled() was introduced by commit:

  c73deb6aecda ("perf/x86: Add ability to calculate TSC from perf sample timestamps")

The only caller was arch_perf_update_userpage(), which had been refactored
by commit:

  d8b11a0cbd1c ("perf/x86: Clean up cap_user_time* setting")

... so no need keep and export it any more.

Signed-off-by: Wei Jiangang <weijg.fnst@cn.fujitsu.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: a.p.zijlstra@chello.nl
Cc: adrian.hunter@intel.com
Cc: bp@suse.de
Link: http://lkml.kernel.org/r/1468570330-25810-1-git-send-email-weijg.fnst@cn.fujitsu.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/include/asm/tsc.h

@@ -35,7 +35,6 @@ extern void tsc_init(void);
 extern void mark_tsc_unstable(char *reason);
 extern int unsynchronized_tsc(void);
 extern int check_tsc_unstable(void);
-extern int check_tsc_disabled(void);
 extern unsigned long native_calibrate_cpu(void);
 extern unsigned long native_calibrate_tsc(void);
 extern unsigned long long native_sched_clock_from_tsc(u64 tsc);

arch/x86/kernel/tsc.c

@@ -335,12 +335,6 @@ int check_tsc_unstable(void)
 }
 EXPORT_SYMBOL_GPL(check_tsc_unstable);
 
-int check_tsc_disabled(void)
-{
-	return tsc_disabled;
-}
-EXPORT_SYMBOL_GPL(check_tsc_disabled);
-
 #ifdef CONFIG_X86_TSC
 int __init notsc_setup(char *str)
 {