trivial: fix typo in bio_alloc kernel doc

Fix typo in bio_alloc kernel doc.
Signed-off-by: NNikanth Karthikesan <knikanth@suse.de>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

fs/bio.c

@@ -358,9 +358,9 @@ static void bio_kmalloc_destructor(struct bio *bio)
  *
  *   If %__GFP_WAIT is set, then bio_alloc will always be able to allocate
  *   a bio. This is due to the mempool guarantees. To make this work, callers
- *   must never allocate more than 1 bio at the time from this pool. Callers
+ *   must never allocate more than 1 bio at a time from this pool. Callers
  *   that need to allocate more than 1 bio must always submit the previously
- *   allocate bio for IO before attempting to allocate a new one. Failure to
+ *   allocated bio for IO before attempting to allocate a new one. Failure to
  *   do so can cause livelocks under memory pressure.
  *
  **/