tracing: make PREEMPTIRQ_EVENTS depend on TRACING

When CONFIG_TRACING is disabled, the new preemptirq events tracer
produces a build failure:

In file included from kernel/trace/trace_irqsoff.c:17:0:
kernel/trace/trace.h: In function 'trace_test_and_set_recursion':
kernel/trace/trace.h:542:28: error: 'struct task_struct' has no member named 'trace_recursion'

Adding an explicit dependency avoids the broken configuration.

Link: http://lkml.kernel.org/r/20171103104031.270375-1-arnd@arndb.de

Fixes: d59158162e03 ("tracing: Add support for preempt and irq enable/disable events")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

kernel/trace/Kconfig

@@ -164,6 +164,7 @@ config PREEMPTIRQ_EVENTS
 	bool "Enable trace events for preempt and irq disable/enable"
 	select TRACE_IRQFLAGS
 	depends on DEBUG_PREEMPT || !PROVE_LOCKING
+	depends on TRACING
 	default n
 	help
 	  Enable tracing of disable and enable events for preemption and irqs.