We don't use it anyway as XGMAC only supports polling for timestamp (in
current SW implementation). This greatly reduces the system load by
reducing the number of interrupts.

Fixes: 2142754f ("net: stmmac: Add MAC related callbacks for XGMAC2")
Signed-off-by: Jose Abreu <Jose.Abreu@synopsys.com>
Signed-off-by: David S. Miller <davem@davemloft.net>