ata: ep93xx: Use proper enums for directions

Clang warns when one enumerated type is implicitly converted to another.

drivers/ata/pata_ep93xx.c:662:36: warning: implicit conversion from
enumeration type 'enum dma_data_direction' to different enumeration type
'enum dma_transfer_direction' [-Wenum-conversion]
        drv_data->dma_rx_data.direction = DMA_FROM_DEVICE;
                                        ~ ^~~~~~~~~~~~~~~
drivers/ata/pata_ep93xx.c:670:36: warning: implicit conversion from
enumeration type 'enum dma_data_direction' to different enumeration type
'enum dma_transfer_direction' [-Wenum-conversion]
        drv_data->dma_tx_data.direction = DMA_TO_DEVICE;
                                        ~ ^~~~~~~~~~~~~
drivers/ata/pata_ep93xx.c:681:19: warning: implicit conversion from
enumeration type 'enum dma_data_direction' to different enumeration type
'enum dma_transfer_direction' [-Wenum-conversion]
        conf.direction = DMA_FROM_DEVICE;
                       ~ ^~~~~~~~~~~~~~~
drivers/ata/pata_ep93xx.c:692:19: warning: implicit conversion from
enumeration type 'enum dma_data_direction' to different enumeration type
'enum dma_transfer_direction' [-Wenum-conversion]
        conf.direction = DMA_TO_DEVICE;
                       ~ ^~~~~~~~~~~~~

Use the equivalent valued enums from the expected type so that Clang no
longer warns about a conversion.

DMA_TO_DEVICE = DMA_MEM_TO_DEV = 1
DMA_FROM_DEVICE = DMA_DEV_TO_MEM = 2

Acked-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>