drivers: net: xgene: fix: Disable coalescing on v1 hardware

Since ethernet v1 hardware has a bug related to coalescing, disabling
this feature.

Signed-off-by: Iyappan Subramanian <isubramanian@apm.com>
Signed-off-by: Toan Le <toanle@apm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>