Revert "unexport bio_{,un}map_user"

Outside users like asmlib uses the mapping functions. API wise, the
export is definitely sane. It's a better idea to keep this export
than to require external users to open-code this piece of code instead.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/fs/bio.c b/fs/bio.c
index 3312fcc..553b5b7 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -1194,6 +1194,8 @@
 EXPORT_SYMBOL(bio_add_page);
 EXPORT_SYMBOL(bio_add_pc_page);
 EXPORT_SYMBOL(bio_get_nr_vecs);
+EXPORT_SYMBOL(bio_map_user);
+EXPORT_SYMBOL(bio_unmap_user);
 EXPORT_SYMBOL(bio_map_kern);
 EXPORT_SYMBOL(bio_pair_release);
 EXPORT_SYMBOL(bio_split);