sata_inic162x: kill now unused bmdma related stuff

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: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>