treewide: Fix typo in Documentation/DocBook

This patch fix spelling typo in Documentation/DocBook.
It is because .html and .xml files are generated by make htmldocs,
I have to fix a typo within the source files.

Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/block/blk-map.c b/block/blk-map.c
index 623e1cd..62382ad 100644
--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -285,7 +285,7 @@
  *
  * Description:
  *    Data will be mapped directly if possible. Otherwise a bounce
- *    buffer is used. Can be called multple times to append multple
+ *    buffer is used. Can be called multiple times to append multiple
  *    buffers.
  */
 int blk_rq_map_kern(struct request_queue *q, struct request *rq, void *kbuf,