sched/clock, x86/perf: Fix "perf test tsc"

People reported that commit:

  5680d8094f ("sched/clock: Provide better clock continuity")

broke "perf test tsc".

That commit added another offset to the reported clock value; so
take that into account when computing the provided offset values.

Reported-by: Adrian Hunter <adrian.hunter@intel.com>
Reported-by: Arnaldo Carvalho de Melo <acme@kernel.org>
Tested-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 5680d8094f ("sched/clock: Provide better clock continuity")
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/kernel/tsc.c

@@ -328,7 +328,7 @@ unsigned long long sched_clock(void)
 	return paravirt_sched_clock();
 }
 
-static inline bool using_native_sched_clock(void)
+bool using_native_sched_clock(void)
 {
 	return pv_time_ops.sched_clock == native_sched_clock;
 }
@@ -336,7 +336,7 @@ static inline bool using_native_sched_clock(void)
 unsigned long long
 sched_clock(void) __attribute__((alias("native_sched_clock")));
 
-static inline bool using_native_sched_clock(void) { return true; }
+bool using_native_sched_clock(void) { return true; }
 #endif
 
 int check_tsc_unstable(void)