sched/fair: Fix documentation file path

The 'tip' prefix probably referred to the -tip tree and is not required,
remove it.

Signed-off-by: Sebastian Andrzej Siewior <[e-mail]>
Acked-by: Peter Zijlstra <[e-mail]>
Cc: Linus Torvalds <[e-mail]>
Cc: Paul Turner <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Ingo Molnar <[e-mail]>

init/Kconfig

···
 	  tasks running within the fair group scheduler.  Groups with no limit
 	  set are considered to be unconstrained and will run with no
 	  restriction.
-	  See tip/Documentation/scheduler/sched-bwc.txt for more information.
+	  See Documentation/scheduler/sched-bwc.txt for more information.
 
 config RT_GROUP_SCHED
 	bool "Group scheduling for SCHED_RR/FIFO"