pata_cs5536: forward port changes from cs5536

* Fix cable detection to also account for the slave device cable bit.

* Disable UDMA when programming MWDMA in cs5536_set_dmamode().

* Don't change UDMA settings in cs5536_set_piomode().

* Add cs5536_program_dtc() helper.

* Cleanup and uninline cs5536_[read,write]() methods.

Cc: Martin K. Petersen <mkp@mkp.net>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>