filesystems: add missing nlink wrappers

Replace direct i_nlink updates with the respective updater function
(inc_nlink, drop_nlink, clear_nlink, inode_dec_link_count).

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 4dc6d07..1fc715a 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -320,7 +320,7 @@
 		memset(&inode->i_ctime, 0, sizeof(inode->i_ctime));
 		inode->i_version = 0;
 		inode->i_size = 0;
-		inode->i_nlink = 0;
+		clear_nlink(inode);
 		inode->i_uid = -2;
 		inode->i_gid = -2;
 		inode->i_blocks = 0;