scsi: NCR5380: Remove redundant result calculation from NCR5380_transfer_pio()

NCR5380_transfer_pio() returns an ambiguous value which is ignored by
callers. Make it void and remove the redundant calculation. Adopt
kernel-doc format for the updated description.

Tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Finn Thain <fthain@linux-m68k.org>
Link: https://lore.kernel.org/r/c07a52d0d7610b4b9969d6dd4fc9a62458fe15de.1723001788.git.fthain@linux-m68k.org


Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>