driver/ldpaa_eth: Add LDPAA Ethernet driver

LDPAA Ethernet driver is a freescale's new ethernet driver based on
Layerscape architecture.

Every ethernet driver controls on DPNI object. Where all DPNIs share
one common DPBP and DPIO object to support  Rx and Tx flows.

Signed-off-by: Prabhakar Kushwaha <prabhakar@freescale.com>
CC: Cristian Sovaiala <cristian.sovaiala@freescale.com>
CC: Bogdan Hamciuc <bogdan.hamciuc@freescale.com>
CC: J. German Rivera <German.Rivera@freescale.com>
[York Sun: s/NetReceive/net_process_received_packet]
Reviewed-by: York Sun <yorksun@freescale.com>