GFS2: Don't use _raw version of RCU dereference

As per RCU glock patch review comments, don't use the _raw
version of this function here.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>