sched: Fix comment about PREEMPT_ACTIVE bit location

PREEMPT_ACTIVE flag is bit 27, not 28. Fix the comment.
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: paulmck@linux.vnet.ibm.com
Cc: josh@joshtriplett.org
Cc: rostedt@goodmis.org
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20120720192459.6149.14821.stgit@srivatsabhat.in.ibm.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

include/linux/hardirq.h

@@ -22,7 +22,7 @@
  *
  * - bits 16-25 are the hardirq count (max # of nested hardirqs: 1024)
  * - bit 26 is the NMI_MASK
- * - bit 28 is the PREEMPT_ACTIVE flag
+ * - bit 27 is the PREEMPT_ACTIVE flag
  *
  * PREEMPT_MASK: 0x000000ff
  * SOFTIRQ_MASK: 0x0000ff00