arinc653: remove idle period in default schedule

By initializing major_frame in a653sched_init(), an idle period was
inadvertently introduced into the default schedule. Account for the
initial value of major_frame when populating the default schedule.

Fixes: f2927d8343 ("xen/arinc653: fix delay in the start of major frame")
Signed-off-by: Stewart Hildebrand <stewart.hildebrand@amd.com>
Reviewed-by: Juergen Gross <jgross@suse.com>

xen/common/sched/arinc653.c

@@ -427,7 +427,8 @@ a653sched_alloc_udata(const struct scheduler *ops, struct sched_unit *unit,
             sched_priv->schedule[entry].runtime = DEFAULT_TIMESLICE;
             sched_priv->schedule[entry].unit = unit;
 
-            sched_priv->major_frame += DEFAULT_TIMESLICE;
+            if ( entry )
+                sched_priv->major_frame += DEFAULT_TIMESLICE;
             ++sched_priv->num_schedule_entries;
         }
     }