[PATCH] namespace: rename _mntput to mntput_no_expire

This patch renames _mntput() to something a little more descriptive:
mntput_no_expire().

Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Acked-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>