sched: Rename sched.c as sched/core.c in comments and Documentation

Most of the stuff from kernel/sched.c was moved to kernel/sched/core.c long time
back and the comments/Documentation never got updated.

I figured it out when I was going through sched-domains.txt and so thought of
fixing it globally.

I haven't crossed check if the stuff that is referenced in sched/core.c by all
these files is still present and hasn't changed as that wasn't the motive behind
this patch.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/cdff76a265326ab8d71922a1db5be599f20aad45.1370329560.git.viresh.kumar@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/avr32/kernel/process.c

@@ -341,7 +341,7 @@ unsigned long get_wchan(struct task_struct *p)
 		 * is actually quite ugly. It might be possible to
 		 * determine the frame size automatically at build
 		 * time by doing this:
-		 *   - compile sched.c
+		 *   - compile sched/core.c
 		 *   - disassemble the resulting sched.o
 		 *   - look for 'sub sp,??' shortly after '<schedule>:'
 		 */