drivers: net: xgene-v2: Add transmit and receive

This patch adds,
    - Transmit
    - Transmit completion poll
    - Receive poll
    - NAPI handler

and enables the driver.

Signed-off-by: Iyappan Subramanian <isubramanian@apm.com>
Signed-off-by: Keyur Chudgar <kchudgar@apm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>