davinci: emac: add new features to autonegotiate for EMAC

add more features like DUPLEX, 100MB link speed etc to auto negotiate
in EMAC driver. EMAC controller autonegotiates for these features with
PHYs which are on the board.

Signed-off-by: Sudhakar Rajashekhara <sudhakar.raj@ti.com>
Signed-off-by: Manjunath Hadli <manjunath.hadli@ti.com>
Signed-off-by: Sandeep Paulraj <s-paulraj@ti.com>