block: mark bio_truncate static

bio_truncate is only used in bio.c, so mark it static.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20211012161804.991559-9-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/block/bio.c b/block/bio.c
index c89e402..d512045 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -546,7 +546,7 @@ EXPORT_SYMBOL(zero_fill_bio);
  *   REQ_OP_READ, zero the truncated part. This function should only
  *   be used for handling corner cases, such as bio eod.
  */
-void bio_truncate(struct bio *bio, unsigned new_size)
+static void bio_truncate(struct bio *bio, unsigned new_size)
 {
 	struct bio_vec bv;
 	struct bvec_iter iter;