net: davinci emac: use dma_{map, unmap}_single API for cache coherency

The davinci emac driver uses some ARM specific DMA APIs
for cache coherency which have been removed from kernel
with the 2.6.34 merge.

Modify the driver to use the dma_{map, unmap}_single() APIs
defined in dma-mapping.h

Without this fix, the driver fails to compile on Linus's
tree.

Tested on DM365 and OMAP-L138 EVMs.

Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Acked-by: Kevin Hilman <khilman@deeprootsystems.com>
Signed-off-by: David S. Miller <davem@davemloft.net>