ata_port_start — Set port up for dma.
int ata_port_start (
struct ata_port * ap)
;
Called just after data structures for each port are initialized. Allocates space for PRD table.
May be used as the port_start
entry in ata_port_operations.
We don't need to allocate DMA buffers if the port is not
DMA capable so we should split this for dma/non dma or make
calling it conditional on it being present.