Before all commands used sg, data_mapping and data_mapped were used to
distinguish whether the command had used map_single or map_sg.  Now all
commands are sg, so we can delete data_mapping, data_mapped and the
wrapper functions __unmap_scsi_data, __map_scsi_sg_data, unmap_scsi_data
and map_scsi_sg_data.
Signed-off-by: NMatthew Wilcox <willy@linux.intel.com>
Signed-off-by: NJames Bottomley <James.Bottomley@SteelEye.com>