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>

mm/shmem.c

@@ -2503,7 +2503,7 @@ struct file *shmem_file_setup(const char *name, loff_t size, unsigned long flags
 
 	d_instantiate(path.dentry, inode);
 	inode->i_size = size;
-	inode->i_nlink = 0;	/* It is unlinked */
+	clear_nlink(inode);	/* It is unlinked */
 #ifndef CONFIG_MMU
 	error = ramfs_nommu_expand_for_mapping(inode, size);
 	if (error)