md: provide appropriate return value for spare_active functions.

md_check_recovery expects ->spare_active to return 'true' if any
spares were activated, but none of them do, so the consequent change
in 'degraded' is not notified through sysfs.

So count the number of spares activated, subtract it from 'degraded'
just once, and return it.

Reported-by: Adrian Drzewiecki <adriand@vmware.com>
Signed-off-by: NeilBrown <neilb@suse.de>
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 76d1fc9..a2f8a71 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -1116,6 +1116,8 @@
 	int i;
 	conf_t *conf = mddev->private;
 	mirror_info_t *tmp;
+	int count = 0;
+	unsigned long flags;
 
 	/*
 	 * Find all non-in_sync disks within the RAID10 configuration
@@ -1126,16 +1128,16 @@
 		if (tmp->rdev
 		    && !test_bit(Faulty, &tmp->rdev->flags)
 		    && !test_and_set_bit(In_sync, &tmp->rdev->flags)) {
-			unsigned long flags;
-			spin_lock_irqsave(&conf->device_lock, flags);
-			mddev->degraded--;
-			spin_unlock_irqrestore(&conf->device_lock, flags);
+			count++;
 			sysfs_notify_dirent(tmp->rdev->sysfs_state);
 		}
 	}
+	spin_lock_irqsave(&conf->device_lock, flags);
+	mddev->degraded -= count;
+	spin_unlock_irqrestore(&conf->device_lock, flags);
 
 	print_conf(conf);
-	return 0;
+	return count;
 }