[GFS2] Set d_ops for root inode

Well, I managed to track down the bug in gfs2 that was causing
my grief.  Below is a patch for the problem.  Please incorporate
as you see fit.  Or should I say: as you see git.

The problem was basically that you never set d_ops for the root
inode, so the wrong hash algorithm was being used.  But only for
the root directory.  Turns out that if I used subdirectories, it
used the proper hash and my files were found just fine.

Signed-off-by: Robert S Peterson <rpeterso@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>