tracing: Fixup logic inversion on setting trace_global_clock defaults

In commit 932066a15335 ("tracing: Default to using trace_global_clock if
sched_clock is unstable"), the logic for deciding to override the
default clock if unstable was reversed from the earlier posting. I was
trying to reduce the width of the message by using an early return
rather than a if-block, but reverted back to using the if-block and
accidentally left the predicate inverted.

Link: http://lkml.kernel.org/r/20180404212450.26646-1-chris@chris-wilson.co.uk

Fixes: 932066a15335 ("tracing: Default to using trace_global_clock if sched_clock is unstable")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

kernel/trace/trace.c

@@ -8602,7 +8602,7 @@ late_initcall_sync(clear_boot_tracer);
 __init static int tracing_set_default_clock(void)
 {
 	/* sched_clock_stable() is determined in late_initcall */
-	if (trace_boot_clock || sched_clock_stable()) {
+	if (!trace_boot_clock && !sched_clock_stable()) {
 		printk(KERN_WARNING
 		       "Unstable clock detected, switching default tracing clock to \"global\"\n"
 		       "If you want to keep using the local clock, then add:\n"