drivers: net: Add APM X-Gene SoC ethernet driver support.

This patch adds network driver for APM X-Gene SoC ethernet.

Signed-off-by: Iyappan Subramanian <isubramanian@apm.com>
Signed-off-by: Ravi Patel <rapatel@apm.com>
Signed-off-by: Keyur Chudgar <kchudgar@apm.com>
Signed-off-by: Dean Nelson <dnelson@redhat.com>
Reviewed-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>