pata_rdc: remove unused variable in rdc_init_one()

The variable port_flags is initialized but never used
otherwise, so remove the unused variable.

dpatch engine is used to auto generate this patch.
(https://github.com/weiyj/dpatch

)

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>