block: reuse part_in_flight_rw for part_in_flight

They are almost identical, to make code cleaner.

Link: https://lore.kernel.org/linux-raid/20250506124903.2540268-2-yukuai1@huaweicloud.com
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: John Garry <john.g.garry@oracle.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>

Author: YuKuai-huawei

block/genhd.c

@@ -125,21 +125,6 @@ static void part_stat_read_all(struct block_device *part,
 	}
 }
 
-unsigned int part_in_flight(struct block_device *part)
-{
-	unsigned int inflight = 0;
-	int cpu;
-
-	for_each_possible_cpu(cpu) {
-		inflight += part_stat_local_read_cpu(part, in_flight[0], cpu) +
-			    part_stat_local_read_cpu(part, in_flight[1], cpu);
-	}
-	if ((int)inflight < 0)
-		inflight = 0;
-
-	return inflight;
-}
-
 static void part_in_flight_rw(struct block_device *part,
 		unsigned int inflight[2])
 {
@@ -157,6 +142,15 @@ static void part_in_flight_rw(struct block_device *part,
 		inflight[1] = 0;
 }
 
+unsigned int part_in_flight(struct block_device *part)
+{
+	unsigned int inflight[2];
+
+	part_in_flight_rw(part, inflight);
+
+	return inflight[READ] + inflight[WRITE];
+}
+
 /*
  * Can be deleted altogether. Later.
  *