[SCSI] ibmvscsi: Remove unnecessary map_sg check

Since sg_tablesize is set appropriately in the scsi host template,
remove the unnecessary check to make sure it is not exceeded
following the dma_map_sg call.

Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>