net: stmmac: Enable support for > 32 Bits addressing in XGMAC

Currently, stmmac only supports 32 bits addressing for SKB. Enable the
support for upto 48 bits addressing in XGMAC core.

This avoids the use of bounce buffers and increases performance.

Changes from v1:
	- Fallback to 32 bits in failure (Andrew)

Signed-off-by: Jose Abreu <joabreu@synopsys.com>
Cc: Joao Pinto <jpinto@synopsys.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Cc: Alexandre Torgue <alexandre.torgue@st.com>
Cc: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/stmicro/stmmac/common.h b/drivers/net/ethernet/stmicro/stmmac/common.h
index 9e8f4db..2403a65 100644
--- a/drivers/net/ethernet/stmicro/stmmac/common.h
+++ b/drivers/net/ethernet/stmicro/stmmac/common.h
@@ -351,6 +351,7 @@ struct dma_features {
 	unsigned int frpsel;
 	unsigned int frpbs;
 	unsigned int frpes;
+	unsigned int addr64;
 };
 
 /* GMAC TX FIFO is 8K, Rx FIFO is 16K */