ata: pata_parport-bpck6: don't cast pi->pardev to struct pardevice *

pi->pardev is struct pardevice *, no need to cast it to the same type.
Also clean up the return mess.

Signed-off-by: Ondrej Zary <linux@zary.sk>
Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>