sched: fix startup penalty calculation

fix task startup penalty miscalculation: sysctl_sched_granularity is
unsigned int and wait_runtime is long so we first have to convert it
to long before turning it negative ...
Signed-off-by: NIngo Molnar <mingo@elte.hu>

kernel/sched_fair.c

@@ -1047,7 +1047,7 @@ static void task_new_fair(struct rq *rq, struct task_struct *p)
 	 * -granularity/2, so initialize the task with that:
 	 */
 	if (sysctl_sched_features & SCHED_FEAT_START_DEBIT)
-		p->se.wait_runtime = -(sysctl_sched_granularity / 2);
+		p->se.wait_runtime = -((long)sysctl_sched_granularity / 2);
 
 	__enqueue_entity(cfs_rq, se);
 }