logfs: remove unnecessary nlink setting

alloc_inode() initializes i_nlink to 1.  Remove unnecessary
re-initialization.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
CC: Joern Engel <joern@logfs.org>
CC: Prasad Joshi <prasadjoshi.linux@gmail.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>