TI Davinci EMAC : Re-use driver for other platforms.

The davinci EMAC peripheral is also available on other TI
platforms -notably TI AM3517 SoC. This patch modifies the
config option and the platform structure header files so that
the driver can be reused on non-davinci platforms as well.

Signed-off-by: Sriramakrishnan <srk@ti.com>
Acked-by: Chaithrika U S <chaithrika@ti.com>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>