[SCSI] zfcp: Remove unnecessary default case and assignments
enum dma_data_direction only has the 4 values DMA_BIDIRECTIONAL,
DMA_TO_DEVICE, DMA_FROM_DEVICE and DMA_NONE. No need to have the
default case. While changing this, setup sbtype in one place to make
sparse happy.
The default value of retval is already -EIO, so remove the
additional assignment for these two cases.