block: fix timeout changes for legacy request drivers

blk_mq_complete_request can only be called for blk-mq drivers, but when
removing the BLK_EH_HANDLED return value, two legacy request timeout
methods incorrectly got switched to call blk_mq_complete_request.
Call __blk_complete_request instead to reinstance the previous behavior.
For that __blk_complete_request needs to be exported.

Fixes: 1fc2b62e ("scsi_transport_fc: complete requests from ->timeout")
Fixes: 0df0bb08 ("null_blk: complete requests from ->timeout")
Reported-by: Jianchao Wang <jianchao.w.wang@oracle.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/block/blk-softirq.c b/block/blk-softirq.c
index 01e2b35..15c1f5e 100644
--- a/block/blk-softirq.c
+++ b/block/blk-softirq.c
@@ -144,6 +144,7 @@
 
 	local_irq_restore(flags);
 }
+EXPORT_SYMBOL(__blk_complete_request);
 
 /**
  * blk_complete_request - end I/O on a request