This enables OSP (Operate on Second Packet) for GMAC4. The feature
allows DMA to fetch second descriptor while its still processing the
first one.
Running iperf, the performance gain is +/- 38%.
Signed-off-by: Jose Abreu <joabreu@synopsys.com> Cc: David S. Miller <davem@davemloft.net> Cc: Joao Pinto <jpinto@synopsys.com> Cc: Vitor Soares <soares@synopsys.com> Cc: Giuseppe Cavallaro <peppe.cavallaro@st.com> Cc: Alexandre Torgue <alexandre.torgue@st.com> Signed-off-by: David S. Miller <davem@davemloft.net>