Documentation: Docbook: Fix generated DocBook/kernel-api.xml

This patch fix spelling typo found in DocBook/kernel-api.xml.
It is because the file is generated from the source comments,
I have to fix the comments in source codes.

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/include/linux/kfifo.h b/include/linux/kfifo.h
index 554fde3..473b436 100644
--- a/include/linux/kfifo.h
+++ b/include/linux/kfifo.h
@@ -722,7 +722,7 @@
 /**
  * kfifo_dma_out_finish - finish a DMA OUT operation
  * @fifo: address of the fifo to be used
- * @len: number of bytes transferrd
+ * @len: number of bytes transferred
  *
  * This macro finish a DMA OUT operation. The out counter will be updated by
  * the len parameter. No error checking will be done.