kernfs: Add noop_fsync to supported kernfs_file_fops

If you edit a kernfs backed file with vi(1), you see an ugly error
message when you write the file because vi tries to fsync(2) the
file after writing, which fails.

We have noop_fsync() for this, use it.
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/kernfs/file.c

@@ -911,6 +911,7 @@ const struct file_operations kernfs_file_fops = {
 	.open		= kernfs_fop_open,
 	.release	= kernfs_fop_release,
 	.poll		= kernfs_fop_poll,
+	.fsync		= noop_fsync,
 };
 
 /**