sched: Fix typo in struct sched_avg member description

Remove extra 'for' from the description about member of
struct sched_avg.

Signed-off-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Cc: pjt@google.com
Cc: peterz@infradead.org
Link: http://lkml.kernel.org/r/20130627060409.GB18582@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

include/linux/sched.h

@@ -924,7 +924,7 @@ struct load_weight {
 struct sched_avg {
 	/*
 	 * These sums represent an infinite geometric series and so are bound
-	 * above by 1024/(1-y).  Thus we only need a u32 to store them for for all
+	 * above by 1024/(1-y).  Thus we only need a u32 to store them for all
 	 * choices of y < 1-2^(-32)*1024.
 	 */
 	u32 runnable_avg_sum, runnable_avg_period;