sched: scheduler debugging, enable in Kconfig

enable CONFIG_SCHED_DEBUG in lib/Kconfig.debug.

the runtime overhead of this option is very small.
Signed-off-by: NIngo Molnar <mingo@elte.hu>

lib/Kconfig.debug

@@ -105,6 +105,15 @@ config DETECT_SOFTLOCKUP
 	   can be detected via the NMI-watchdog, on platforms that
 	   support it.)
 
+config SCHED_DEBUG
+	bool "Collect scheduler debugging info"
+	depends on DEBUG_KERNEL && PROC_FS
+	default y
+	help
+	  If you say Y here, the /proc/sched_debug file will be provided
+	  that can help debug the scheduler. The runtime overhead of this
+	  option is minimal.
+
 config SCHEDSTATS
 	bool "Collect scheduler statistics"
 	depends on DEBUG_KERNEL && PROC_FS