block: Export blk_poll

The new NVMe over fabrics target will make use of this outside from a
module.

Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/block/blk-core.c b/block/blk-core.c
index db31a29..dd32563 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -3385,6 +3385,7 @@
 
 	return false;
 }
+EXPORT_SYMBOL_GPL(blk_poll);
 
 #ifdef CONFIG_PM
 /**