net: ethernet: ti: davinci_cpdma: use dma_addr_t for desc_mem_phys and desc_hw_addr

Use dma_addr_t for desc_mem_phys and desc_hw_addr to avoid types
conversions.

Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>