xfs: Add xfs_iget_root() to XFS filesystem ops
This patch adds initial implementation of the xfs_iget_root() filesystem
operation.
Note also that this is not going to work with inode B+trees with any
level associated with it other than only leafs in the tree. I intend to
finish these remaining features in xfs_iget_root() once I get xfs_iget()
function working properly.
I'm looking forward to implement xfs_iget() function since we have now
xfs_iget_root() function at some point.
Signed-off-by: Paulo Alcantara <pcacjr@zytor.com>