sata_inic162x doesn't use BMDMA anymore.  Kill bmdma related stuff.

* prdctl manipulation

* port IRQ mask manipulation

* inherit ATA_BASE_SHT instead of ATA_BMDMA_SHT

* BMDMA methods
Signed-off-by: NTejun Heo <htejun@gmail.com>
Signed-off-by: NJeff Garzik <jgarzik@redhat.com>