ata: pata_parport-bpck6: remove useless range check from read/write_regr

bpck6_read_regr() and bpck6_write_regr() check values of cont and reg
but there's no point in doing that. They can only be called with
a fixed set of values. Remove the checks.

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>