xfs: Add helper function xfs_attr_node_removename_rmt

This patch adds another new helper function
xfs_attr_node_removename_rmt. This will also help modularize
xfs_attr_node_removename when we add delay ready attributes later.

Signed-off-by: Allison Collins <allison.henderson@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Chandan Rajendra <chandanrlinux@gmail.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Acked-by: Dave Chinner <dchinner@redhat.com>