drivers: net: xgene-v2: Add base driver

This patch adds,

     - probe, remove, shutdown
     - open, close and stats
     - create and delete ring
     - request and delete irq

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>