[SCSI] eata: fix the data buffer accessors conversion regression

This fixes the regression introduced by the commit
58e2a02e (eata: convert to use the
data buffer accessors), reported:

http://marc.info/?t=122987621300006&r=1&w=2



- fix DMA_NONE handling in map_dma()

- this driver can't use scsi_dma_map since host->shost_gendev.parent
is not set properly (it uses scsi_register).

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Reported-by: Arthur Marsh <arthur.marsh@internode.on.net>
Tested-by: Arthur Marsh <arthur.marsh@internode.on.net>
Cc: stable@kernel.org
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>