namei: fix warning while make xmldocs caused by namei.c

Fix the following warnings:

Warning(.//fs/namei.c:2422): No description found for parameter 'nd'
Warning(.//fs/namei.c:2422): Excess function parameter 'nameidata'
description in 'path_mountpoint'

Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/namei.c

@@ -2438,7 +2438,7 @@ done:
 
 /**
  * path_mountpoint - look up a path to be umounted
- * @nameidata:	lookup context
+ * @nd:		lookup context
  * @flags:	lookup flags
  * @path:	pointer to container for result
  *