ARM: DaVinci: EMAC: Memory mapping simplified, use the updated platform data

The memory mapping has been modified to remove the multiple mappings and
this simplifies the error handling in probe.
The PHY mask information from the platform is utilized instead of the
hardcoded values in the driver. Similarly the max MDIO clock value is
from platform data.
Signed-off-by: Chaithrika U S <chaithrika@ti.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>